Undefined color model when colorlinks defined in class file

[jankapunkt]

I'm using a template .cls that defines hyperref with the following attributes:

% ...
\RequirePackage{color}
\definecolor{foo}{rgb}{.5,.5,.5}
\RequirePackage[colorlinks=true,linkcolor=foo,citecolor=foo,filecolor=foo,menucolor=foo,urlcolor=foo]{hyperref}
% ...

This is primarily to auto-color URLs.

I'm using orcidlink like this:

\documentclass{bar}
\usepackage{orcidlink}
\begin{document}
   Look:  \orcidlink{0009-0008-8088-9837}
\end{document}

Leading to the error ! Package xcolor Error: Undefined color model '.`

When changing the hyperref option to colorlinks=false it will work, however I can't change the options as it affects the entire link formatting of the document.

Any ideas how solve this?

[shinhyungyang]

@jankapunkt I changed the class file:

-\RequirePackage{color}
-\definecolor{foo}{rgb}{.5,.5,.5}
+\RequirePackage{xcolor}
+\definecolor{foo}{HTML}{0D0D0D}

[duetosymmetry]

@jankapunkt @shinhyungyang sorry that I missed this back in May of 2025! TikZ requires the package xcolor. I don't know how the package color interacts with xcolor if you try to load both of them. Switching to using xcolor will of course avoid your problem. But it would also be nice for other package authors to know if there is some incompatibility, so they know if they can use orcidlink with color if they really want to.