Colors
    Hammering some sense into those content-makers

Your website probably has a color-scheme. Green on white, purple on yellow,
whatever. When you give users the ability to style their content, you may
want them to keep in line with your styling. If you're website is all
about light colors, you don't want a user to come in and vandalize your
page with a deep maroon.

This is an extremely silly feature proposal, but I'm writing it down anyway.

What if the user could constrain the colors specified in inline styles? You
are only allowed to use these shades of dark green for text and these shades
of light yellow for the background. At the very least, you could ensure
that we did not have pale yellow on white text.

Implementation issues:
1. Requires the color attribute definition to know, currently, what the text
and background colors are. This becomes difficult when classes are thrown
into the mix.
2. The user still has to define the permissible colors, how does one do
something like that?