I believe white is 0x00ffffff so black would be 0x00000000.
However, if you still have the override options checked in the skin options then these colours will be ignored.
Also, just to clarify, these colour options only work in MM2.5
If you want to contribute MediaMonkey skins, themes, icons, etc...
It's better if you include images as well as the odd/even colours, because that way you are making it better for MM2.5 without removing functionality for MM2.4