I agree, paint the walls whatever color you want but the ceiling must be white.
And for the record, if you do crown molding don't paint the walls in a color that will cause the molding to be lost.
Crown molding is like bling and should stand out, if it does not then it's not worth putting up.
Edit: Zues pointed out the white crown molding, ya he's right, the white ceiling will wash that out.
I guess you are stuck with an off white for the ceiling, the bling thing still stands, why else would one put up crown molding?