If you always thought green text on a pink background was the ideal color combination then you can use these parameters to make your dreams come true. Here you can define the color of just about any GUI element in Cinema 4D. Colors can be saved to individual schemes (Interface tab).
You should however make sure that the colors you select result in legible menus, etc. In the worst case you can make Cinema 4D "unusable" if you select colors that result in menus that cannot be read. If this should happen simply delete the Cinema 4D.prf and *.col files (e.g., "dark.col" for the dark color scheme) in your user directory’s "prefs" folder. Cinema 4D will then restart with the default color scheme.