Oh yes, the X-colors! For the time being I just read as much as I can find about those colors, because my male cat may be a bearer of the genes for such colors - his great great grandmother being Wildwood's Humla, and it is also possible that my female is a bearer, as she descends from Norodden Eirik BlodÃ¸ks and Maia av Moltemyr (great grandparents). This couple had at least three kittens with chocolate color in different litters.
But as the enigma is not solved as to which genes are involved, there is not much one can do other than just wait and see what happens. But it is interesting, and I suppose these colors will be approved sooner or later.
I have never actually seen an x-colored NFO though, only pictures.