Define New Color in LaTeX – Custom Color Definitions

color

I'm using

\usepackage[dvipsnames]{xcolor}

to use RoyalPurple color, but now I wanted to redefine it to

\definecolor{light-RoyalPurple}{RoyalPurple}{0.85}

But I get

! Package xcolor Error: Undefined color
model `RoyalPurple'.

that doesn't happen with

\definecolor{light-gray}{gray}{0.85}

So I think that \definecolor just works with "normal" colors… how to solve it?

Best Answer

It's not working because you're giving the command an unexpected value. The second argument of \definecolor expects one of the color models from this list:

natural, rgb, cmy, cmyk, hsb, gray, RGB, HTML, HSB, Gray

That's why gray worked in your case. Try replacing that with blue and you'll get the same error. If you want a lighter version of RoyalPurple, use \colorlet.

Output

enter image description here

Code

\documentclass[margin=10pt]{standalone}
\usepackage[dvipsnames]{xcolor}

\colorlet{lRP}{RoyalPurple!85} 

\begin{document}\Huge\bfseries
Black \textcolor{lRP}{Light} \textcolor{RoyalPurple}{Regular} 
\end{document}

Related Solutions

[Tex/LaTex] Light Gray color in beamer

A simple solution would be to use some predefined gray color and the ! syntax together with \colorlet; for example:

\colorlet{shadecolor}{gray!40}

(40% gray and 60% white); increasing the value used will produce darker shades and decreasing it, lighter ones.

[Tex/LaTex] Undefined color error in Section after defining the color

You need to use \protect\grn or else \grn is expanded to \color{NGREEN} when the section heading is converted to upper case.

\documentclass{revtex4}
\usepackage{color}
\definecolor{ngreen}{rgb}{0.2,0.7,0.2}%161
\newcommand{\grn}{\color{ngreen}}
\begin{document}
\section{\protect\grn This is a section}
\end{document}

This is not specific to revtex except in that revtex capitalises section headings. To cause the same problem in any document class you can use

\MakeUppercase{\grn abc}

and the solution (\protect) is the same.