Package `xcolor' by Dr. Uwe Kern
https://github.com/latex3/xcolor/issues

History
=======
2024/09/29 v3.02
* remove definitions of color groups as they are already in the kernel.

2024/09/17
* unknown model error handled (issue #1)

2024/03/13
* Add \relax after \ProcessKeyOptions to improve error context lines

2023/11/15 v3.01
* only warn and not error if obsolete option usenames is used, issue #31

2023/11/11 v3.00
* If a LaTeX older than 2022-06-01 is detected a frozen version is used.
  All new features apply only if LaTeX 2022-06-01 or newer is detected.
  The frozen version can also be requested with \usepackage{xcolor}[=v2]. 
* The new LaTeX key/val handler is used for the package options. That means there
  will be fewer option clash errors, issue #29
* The \rowcolors command has moved to the colortbl package
* The fixpdftex option is obsolete and does nothing at all (issue #20)
* Extended \normalcolor to set also the "dot" color, issue #19
* Fix Gray color model, issue #23

2022/06/12 v2.14
* New features:
    - Load if it exists the code from LaTeX to define \mathcolor.
* Bugfixes (LaTeX Team)
    - Modify \XC@info to avoid spurious error from \colorlet{foo}{} issue #12
    - make \normalcolor, \colorbox, \fcolorbox \textcolor, \pagecolor, 
      \nopagecolor, \definecolor, \DefineNamedColor protected as in color.sty issue #17

2021/10/31 v2.13
* Bugfixes (LaTeX Team)
    - use \@backslashchar color rather than \string\color to
	generate internal csnames, to avoid relying on the
	current setting	of \escapechar
    - Declare dvisvgm option to match graphics and color packages.
	Make dvipdfm an alias for dvipdfmx
    - Modify \XC@info to avoid spurious text from \colorlet{foo}{.!50}

2016/05/11 v2.12
* New features:
    - \nopagecolor command as introduced in `color' v1.1a
      (example added to xcolor3.tex);
    - `luatex' driver option (code provided by DPC) to fix
      incompatibilities due to changes in new LuaTeX version.
* Bugfixes:
    - possible name conflict by \XC@ifxcase call;
    - incorrect internal \@hex@@Hex macro.

2007/01/21 v2.11
* New features:
    - color names `lime' and `teal' added to the set of predefined
      colors.
* Bugfix:
    - incorrect \XC@strip@comma call within `hyperref'-related options.

2006/11/28 v2.10
* New features:
    - `fixinclude' option prevents dvips from explicitly resetting
      current color to `black' before actually inserting an .eps file
      via \color{red}\includegraphics{foo}.
* Changes:
    - \colorbox and \fcolorbox made robust;
    - obsolete package option `pst' removed;
    - several changes to internal macros.
* Bugfixes:
    - incorrect processing of cmyk-type current color `.'.

2005/12/21 v2.09
* New features:
    - \definecolor and \color now accept space-separated color
      specifications, e.g., \color[rgb]{1 .5 0};
    - experimental `xcdraw' option extended to `pdftex' and `dvipdfm'
      drivers.
* Changes:
    - test file xcolor2.tex made compatible with recent changes in
      `pstricks';
    - test file xcolor3.tex extended;
    - driver test file xcolor4.tex extended to demonstrate the different
      frame drawing approaches;
    - more efficient implementation of driver-specific code.

2005/11/25 v2.08
* New features:
    - more flexibility for \fcolorbox arguments, e.g.,
      \fcolorbox[gray]{0.5}[wave]{580}{test};
    - \boxframe returns a frame of given dimensions;
    - new implementation of \f(rame)box and \fcolorbox as an extension
      of bug report latex/3655 to reduce pixel positioning errors in
      output devices;
    - `kernelfbox' option for those who prefer the previous \f(rame)box
      approach;
    - experimental `xcdraw' option uses PostScript commands to draw
      frames and color boxes in case of `dvips'.
* Bugfixes:
    - insufficient expression type detection within \colorlet;
    - wrong calculation in the unit interval reduction for negative
      integers (affecting color series and extended color expressions).

2005/11/12 v2.07
* New features:
    - color model `Hsb' allows to specify hue in degrees;
    - color model `tHsb' (`tuned Hsb') for user-defined hue
      configuration on color wheels;
    - easy generation of color harmonies derived from `Hsb' or `tHsb'
      color wheels, e.g., \color{red>wheel,1,12} yields an `analogous'
      color to `red' on a 12-spoke wheel;
    - additional 317 predefined color names according to rgb.txt, which
      is part of Unix/X11 distributions;
    - `svgnames' option extended by 4 colors taken from rgb.txt;
    - enhanced syntax for immediate conversion, e.g.,
      \definecolor{foo}{rgb:gray}{0.3} or \color[rgb:wave]{478};
    - \@ifundefinedcolor and \@ifundefinedmodel commands.
* Changes:
    - enhanced documentation;
    - several changes to internal macros.
* Bugfixes:
    - wrong calculation of color series components in some cases of
      negative step parameters.

2005/10/15 v2.06
* New features:
    - color model `wave' for (approximate) visualisation of light
      wavelengths, still somewhat experimental;
    - pseudo-model `ps' for colors defined by literal PostScript code
      in conjunction with `pstricks and `dvips'; an illustrative
      example for a gamma-correction approach is given in xcolor2.tex;
    - \substitutecolormodel command for replacement of missing or
      faulty driver-specific color models;
    - improved detection and handling of driver-specific color models;
    - `dvipdfmx' and `xetex' options to support these drivers;
    - generic driver test file xcolor4.tex.
* Changes:
    - \XC@strip@comma doesn't generate a trailing space anymore, which
      improves also the output of the `testcolors' environment.

2005/09/30 v2.05
* New features:
    - `testcolors' environment helps to test colors in different models,
      showing both the visual result and the model-specific parameters;
    - \extractcolorspecs puts model/color specification into two
      separate commands, as opposed to \extractcolorspec;
    - color names `pink' and `olive' added to the set of predefined
      colors.
* Bugfixes:
    - \definecolor{foo}{named}{bar} did not work in v2.04.

2005/09/23 v2.04
* New features:
    - preparation for usage of additional - driver-provided - color
      models;
    - `pstricks' users may now specify explicit color parameters within
      \psset and related commands, e.g., \psset{linecolor=[rgb]{1,0,0}};
      an illustrative example is given in xcolor2.tex.
* Changes:
    - color model names sanitized (i.e., turned to catcode 12)
      throughout the package;
    - \@namelet command deprecated because of name clash with
      `memoir' - please use \XC@let@cc instead
      (more \XC@let@.. commands are available as well);
    - simplified color conversion code by using the new \XC@ifxcase
      command;
    - some minor changes to internal macros.

2005/06/06 v2.03
* New features:
    - `fixpdftex' option loads `pdfcolmk' package in order to improve
      pdfTeX's color behaviour during page breaks.
* Changes:
    - some minor changes to internal macros.
* Bugfixes:
    - due to an incorrect \if statement within \XC@info, \colorlet
      caused trouble whenever its second argument started with two
      identical letters, e.g., \colorlet{rab}{oof};
    - argument processing of \XC@getcolor caused incompatibility with
      `msc' package;
    - `prologue' option caused incompatibility with `preview' package.

2005/03/24 v2.02
* New features:
    - \aftergroupedef command to reproduce \aftergroupdef's behaviour
      prior to v2.01;
    - xcolor's homepage www.ukern.de/tex/xcolor.html now provides also
      a ready-to-run TDS-compliant archive containing all required
      files.
* Changes:
    - \rowcolors and friends are solely enabled by the `table' option;
    - \@ifxempty changed back to more robust variant of v2.00.
* Bugfixes:
    - \psset{linecolor=\ifcase\foo red\or green\or blue\fi} did not work
      with `pstricks' (error introduced in v2.01).

2005/03/15 v2.01
* New features:
    - `prologue' option for comprehensive `named' color support in
      conjunction with `dvips': on-the-fly generation of PostScript
      prologue files with all color definitions, ready for dvips
      inclusion and/or post-processing with device-specific parameters
      (e.g., spot colors);
    - dvips prologue file xcolor.pro to support additional `named'
      colors;
    - \colorlet may now also be used to create named colors from
      arbitrary color expressions;
    - enhanced color definition syntax to allow for target-model
      specific color parameters, e.g.,
      \definecolor{red}{rgb/cmyk}{1,0,0/0,1,1,0}, facilitating the
      usage of tailor-made colors both for displays and printers;
    - `deferred definition' of colors: \preparecolor and
      \definecolors enable decoupling of color specification and control
      sequence generation, especially useful (= memory saving) for large
      lists of colors, of which only a few names are actually used;
    - `dvipsnames*' and `svgnames*' options to support deferred
      definition.
* Changes:
    - higher accuracy: most complement calculations are now exact for
      all 5-digit decimals;
    - \rangeRGB and similar variables may now be changed at any point
      in a document;
    - \aftergroupdef now performs only a first-level expansion of its
      code argument;
    - \XCfileversion and similar internal constants removed from .sty
      and .def files;
    - improved memory management (reduced generation of `multiletter
      control sequences' by \@ifundefined tests);
    - several internal macros improved and/or renamed.
* Bugfixes:
    - \XC@getcolor could cause unwanted spaces when \psset was used
      inside |pspicture| environments (`pstricks');
    - arithmetic overflow could happen when too many decimal digits
      were used within color parameters, e.g., as a result of `fp'
      calculations.

2004/07/04 v2.00
* New features:
    - extended functionality for color expressions: mix colors like a
      painter;
    - support for color blending: specify color mix expressions that
      are being blended with every displayed color;
    - \xglobal command for selective control of globality for color
      definitions, blends, and masks;
    - multiple step operations (e.g., \color{foo!!+++}) and access to
      individual members (e.g., \color{foo!![7]}) in color series;
    - \providecolor command to define only non-existent colors;
    - \definecolorset and \providecolorset commands to facilitate the
      construction of color sets with common underlying color model;
    - additional 147 predefined color names according to SVG 1.1
      specification;
    - `xpdfborder' key for setting the width of hyperlink borders in a
      more driver-independent way if `dvips' is used.
* Changes:
    - `color' package now completely integrated within `xcolor';
    - `override', `usenames', `nodvipsnames' options and \xdefinecolor
      command no longer needed;
    - `dvips' and `dvipsnames' options now independent of each other;
    - \tracingcolors's behaviour changed to make it more versatile and
      reduce log file size in standard cases;
    - \rdivide's syntax made more flexible (divide by numbers and/or
      dimensions);
    - code restructured, some internal commands renamed;
    - documentation rearranged and enhanced.
* Bugfixes:
    - \definecolor{foo}{named}{bar} did not work (error introduced in
      v1.11);
    - more robust behaviour of conditionals within `pstricks'
      key-values.

2004/05/09 v1.11
* New features:
    - switch \ifglobalcolors to control whether color definitions are
      global or local;
    - option `hyperref' provides color expression support for the
      border colors of hyperlinks, e.g.,
      \hypersetup{xurlbordercolor=red!50!yellow};
    - internal hooks \XC@bcolor, \XC@mcolor, and \XC@ecolor for
      additional code that has to be executed immediately before/after
      the current color is being displayed.
* Changes:
    - \XC@logcolor renamed to \XC@display, which is now the core color
      display command;
    - improved interface to `pstricks'.

2004/03/27 v1.10
* New features:
    - support for `named' model;
    - support for `dvips' colors
      (may now be used within color expressions);
    - internal representation of `ordinary' and `named' colors merged
      into unified data structure;
    - allow multiple `-' signs at the beginning of color expressions.
* Bugfixes:
    - commands like \color[named]{foo} caused errors when color masking
      or target model conversion were active;
    - incompatibility with `soul' package: commands \hl, \ul, etc.
      could yield unexpected results.
* Documentation:
    - added formula for general color expressions;
    - enhanced text and index;
    - removed dependence of index generation on local configuration
      file.

2004/02/16 v1.09
* New features:
    - color model `HTML', a 24-bit hexadecimal `RGB' variant;
      allows to specify colors like \color[HTML]{AFFE90};
    - color names `orange', `violet', `purple', and `brown' added to
      the set of predefined colors.
* New xcolor homepage: www.ukern.de/tex/xcolor.html
* Bugfix: \xdefinecolor sometimes did not normalise its parameters.
* Changes:
    - slight improvements of the documentation;
    - example file xcolor1.tex reorganised and abridged.

2004/02/04 v1.08
* New commands/features:
    - \selectcolormodel to change the target model within a document;
    - \adjustUCRBG to fine-tune undercolor-removal and
      black-generation during conversion to `cmyk'.
* Bugfix: color expressions did not work correctly in connection with
  active `!' character, e.g., in case of \usepackage[frenchb]{babel}.
* Code re-organisation:
    - \XC@xdefinecolor merged into \xdefinecolor, making the first
      command obsolete;
    - several internal commands improved/streamlined.

2004/01/20 v1.07
* New feature: support for color masking and color separation.
* New commands:
    - \rmultiply to multiply a dimension register by a real number;
    - \xcolorcmd to pass commands that are to be executed at the end
      of the package.
* Changes:
    - more consistent color handling: extended colors now always take
      precedence over standard colors;
    - several commands improved by using code from the LaTeX kernel.
* Documentation: some minor changes.
* Example files: additional `pstricks' examples (file xcolor2.tex).

2003/12/15 v1.06
* New feature: extended color expressions, allowing for cascaded mix
  operations, e.g., \color{red!30!green!40!blue}.
* Documentation: new section on color expressions.
* Bugfix: color series stepping did not work correctly within
  non-displaying commands like \extractcolorspec{foo!!+}
  (this bug was introduced in v1.05).
* Renamed commands: \ukfileversion and similar internal constants
  renamed to \XCfileversion etc.
* Removed commands: \ifXCpst and \ifXCtable made obsolete by a simple
  trick.

2003/11/21 v1.05
* Bugfixes:
    - package option `hideerrors' should now work as expected;
    - usage of `.' in the first color expression in a document caused
      an error due to incorrect initialisation.
* Code re-organisation: \extractcolorspec now uses \XC@splitcolor,
  making \XC@extract obsolete.

2003/11/09 v1.04
* New feature: easy access to current color within color expressions.
* New option: `override' to replace \definecolor by \xdefinecolor.
* New command: \tracingcolors for logging color-specific information.

2003/09/21 v1.03
* Change: bypass strange behaviour of some drivers.
* New feature: driver-sharing with `hyperref'.

2003/09/19 v1.02
* Change: \extractcolorspec and \colorlet now also accept color series
  as arguments.

2003/09/15 v1.01
* New feature: \definecolorseries and friends.
* Documentation: removed some `doc'-related side-effects.
* Code re-organisation: all calculation-related tools put to one place.
* Bugfixes:
    - \@rdivide: added \relax to fix problem with negative numerators;
    - \rowc@l@rs: replaced \@ifempty by \@ifxempty.

2003/09/09 v1.00
* First published release.