\documentclass{testsuite} \usepackage{fontspec} \usepackage{xcolor} \begin{document} {\fontspec[Color=5500FF]{Verdana}Test} {\fontspec[Color=red]{Verdana}Test} vs {\color{red}\fontspec{Verdana}Test} \definecolor{Foo}{rgb}{0.3,0.4,0.5} {\fontspec[Color=Foo]{Verdana}Test} vs {\color{Foo}\fontspec{Verdana}Test} \end{document}