There is a constant battle between people who want HTML to remain true
to the SGML "idea" and those that want to turn it into a variant of X
and/or TeX. To specify colors is contrary to the spirit of HTML as a
kind of SGML. The idea is that if we let people get down to minute
rendering details with HTML, it will no longer be a one-size-for-all
system, and it will no longer be easy to write and manipulate.
Just some thoughts.