function to get inverse color name?

[unfrostedpoptart]

Hi all.

I'm doing a major overhaul of my emacs 24 init.el files.  I'm trying to convert 
a lot of faces from dark to light to set up alternate themes.  I know I can 
just invert everything with invert-all-faces, but I want to do them 
individually and have the correct name.

Does anyone have a function that takes a named color (e.g. "Red") and returns 
the inverse?  I guess it would convert the name to RRGGBB, subtract each 8-bit 
value from 256, and then convert back to a name.

Thanks for any help and/or pointers to useful functions!

 David