I beleive your getting confused here which admin section you are speaking about here cause our stylesheet editor only edits our stylesheets and there is no maintitle class in our stylesheets.
I know what your doing though cause I just fixed your forum again. You keep deleting the trailing ; when you put a new color in there for maintitle in your forum admin style manager.
To change a color on the ibp stylesheet you go to forum admin look&feel. You then go to the ibp default skin and change the color code. Make sure you do not delete the trailing semicolon. Your only replacing the hex code. Then go to skin tools and rebuild the cache.
Thats all there is to it
You ibp support forums should have some facts how to use there styles menu.