Recently, I have been doing a fair amount of work with fonts and colours  (or color depending if you were not born under british rule).   During this work, I discovered a colour that I didn't know existed.  The color is "transparent".  In .Net world, this color will allow the underlying color to be shown.  Brillant!

So where does this come in very handy -- well consider things like border colours -- often the border colour is pre-defined and you are allowed to change it, but in the world of DNN and skinning, what is the correct colour today, may be horrible when you re-skin your site.  In this case, transparent works perfectly.  Instead of a colour - either a colour number or explicit colour name, use "transparent" and the problem is solved.

While this is no doubt known in the work of designers and skinner, this may be "news" to us more graphically challenged types.

Hope this helps
Paul.

EDIT: Seems that IE6 and probably lower version will default "transparent" to black.  Ugh!   The designers and skinner probably knew that...