I have seen topics in various forums around where users have dyed white\beige keyboards to make them any colour. It would be really cool if we were able to get the casings (and maybe keycaps too while we're at it) in white plastic so that the dye will go to the exact color we want .

That sounds useful, unfortunately I am unfamiliar or the pros and cons of plastic dyes vs paint.
Only advantage I am aware of in dying is that the color does not flake, chip or peel, and dyed color is alot harder to wear off