improvements to color validation in

matplotlib.rcsetup.validate_color() currently regards a variety of
invalid color strings as valid. I created a patch (relative to
matplotlib 0.91.2) that improves the validation performed by said
function. Ought I post it here? I tried to post it as a bug on
SourceForge, but the site refused the upload with a message indicating
the size limitation of bug attachments even though my patch is well
within that limit.