Missing xcolor names

[krlmlr]

xcolor names are a source of pain, because the LaTeX template loads xcolor before evaluating header-includes, and it seems impossible to load default color names after xcolor is loaded -- AFAICT it only supports the option interface, there's no command to load the default color sets.

Can we unconditionally include

\PassOptionsToPackage{dvipsnames,svgnames*,x11names*}{xcolor}

in the default LaTeX template, and perhaps add additional customization points that are evaluated at the beginning of the document and right after \documentclass{}?

[tarleb]

Closing in favor of #6109.