On Thu, Feb 03 2011, Drew Adams wrote:

> FWIW, for this I simply use the complements of the light-background default
> colors as the dark-background colors.  That is not necessarily ideal, but it at
> least is reasonable and consistent.  It is also very quick to do, given some
> code (e.g. hexrgb.el or palette.el) that quickly gives you color complements.

color.el included in Emacs 24 as `color-complement' so you can even use
it in your defface directly, I think.

-- 
Julien Danjou
❱ http://julien.danjou.info