Oh, the CB will darken a bit, and show some dirt after a while. That's part of the charm. Its kind of like an ivory folder or the older ivory micarta in that it takes on a kind of patina. The knife is supposed to be used, and after a while- at least from the knives I'VE seen- it kinda gets that "if only this knife could talk" kinda look to it. Very classy if you ask me. I'm sure it could be cleaned up nicely though! Let us know what you think when you get it.
Oh, and a note on the RG, when that gets dirty from grease I don't think it looks as nice as the CB, but the RG IS very pretty!