What you could do is define those as classes in your stylesheet and then ask people to use something like
etc. That's a cleaner way of doing this anyway, since it would allow you to adjust colors later, in case you want to change your site's theme.
Yes, stylesheet is a way to do it.
Text color is not the most used on any site, but when white text on a black background is required and the editor can do this inline, its too bad the editor and filter aint compatible.