# Situation

Let's say I have defined some colors. I'd like to produce a test page that functions as a color-key for developers.

# Example

The defined colors colora, colorb, and colorc should be iterated without mentioning them explicitly again (happens automatically). This is efficient programming in that I can have an arbitrary number of colors (perhaps 50 or so) and create a time-saving color key.

\documentclass{article}
\usepackage{fontspec}
\usepackage{tikz}
\usepackage{pgffor}

\definecolor{colora}{cmyk}{0,.5,1,.3}
\definecolor{colorb}{cmyk}{.4,.6,.5,.1}
\definecolor{colorc}{cmyk}{.6,.2,.5,.2}

\begin{document}

%\foreach \definedcolor in {defined colors} % pseudo-code
%   \tikz \node [fill=definedcolor, minimum width=2cm, minimum height=1cm,text=white] {name of defined color}; % pseudo-code
\color{colora} COLORA

\color{colorb} COLORB

\color{colorc} COLORC
\end{document}

• Should any pre-defined named colors (such as blue, red, cyan, etc.) be included or excluded from this loop? What if your color definitions overwrite a pre-defined color name? Mar 29 '15 at 19:32

One possible way is to intercept the color definition with your own macro.

\documentclass{article}
\usepackage{tikz}

\def\appendcolor#1#2#3{%
\csname pgfutil@ifundefined\endcsname{definedcolorsofar}{\def\definedcolorsofar{#1}}{%
\expandafter\def\expandafter\definedcolorsofar\expandafter{\definedcolorsofar,#1}}%
\definecolor{#1}{#2}{#3}%
}

\appendcolor{colora}{cmyk}{0,.5,1,.3}
\appendcolor{colorb}{cmyk}{.4,.6,.5,.1}
\appendcolor{colorc}{rgb}{1,0,0}
\appendcolor{colord}{rgb}{0,0,1}

\begin{document}
\tikz{
\foreach \x[count=\xi] in \definedcolorsofar
\node at (0,\xi)[fill=\x, minimum width=2cm,
minimum height=1cm,text=white] {\x};
}

\end{document}


• Could you please explain \csname pgfutil@ifundefined\endcsname? Apr 9 '15 at 13:29
• @macmadness86 Normally if a control sequence has @ character in it you have to put the code inside \makeatletter...\makeatother pair (if it is a package LaTeX handles behind the scene). But if you only have a few of those you can place it within \csname...\endcsname and it will handle it automatically such that you don't need to change the catcode of @. \pgfutil@ifdefined is an if syntax and checks whether the macro has been defined already or not. So if not defined I create, if already exists I append there. Apr 9 '15 at 13:42
• I know this question is old, but I just had a request for putting the cmyk values explicitly on the page. Is that also possible with a minor adjustment to the code? Aug 14 '15 at 12:42
• @macmadness86 I think I didn't get exactly the additional requirement can you elaborate a bit? Aug 14 '15 at 18:13
• For example, if I wanted not just "colora" to be printed, but also cymk and its values: {cmyk}{0,.5,1,.3} either decimally like that or in percentages. The reason for this is that I am designing a style sheet, where the outputted PDF can be used as a reference for other users who might want to user a color. They can then easily reference the cmyk values. Aug 16 '15 at 21:07