AFAIK, the case is a different material to the keycaps and will not accept dye very well or easily, so be careful with that.
I believe fohat.digs has some experience with this and that he paints his cases rather than dying.
The keycaps accept dye amazingly well. The newer Rit dyes are apparently a different formulation and don't work as well as the old version. I have read that iDye Poly is a good one to use.