Setting window colors in the Registry

This is sort of related to my other post about forcing Registry updates.

I've found in the Registry [HKCU\Control Panel\Colors] where the various
window parameters are defined. (Example: ActiveTitle, GradientActiveTitle,
TitleText, etc.)

I've also found [HKU\.DEFAULT\Control Panel\Appearance\Schemes] where the
different schemes are defined, but it's all in Hexadecimal.

Does anyone know how I can define a new scheme to add to that list?
(Obviously I can copy & paste a value and rename it, but how do I edit the
window colors, & etc?)

Thanks much!

Warm regards,

Jim