The last couple of new hair color genes modify the pattern of pigment on the cat. The first is the Inhibitor gene. The dominant I gene masks the background pigment on agouti hairs, making it white. This leads to a ‘silver’ tabby, where the space between the stripes is almost white. This is due to the background color on the agouti hairs being white instead of greyish, or orange for a cat with a lot of rufousing. This leads to a cat that looks a lot like a white tiger. The inhibitor is a dominant gene, the recessive i/i combination gives a normal coloring, which is the most common.
A second modifier gene is the Wideband gene, Wb. When this dominant gene is present, the pigment stops being laid down partway down the hair shaft on all hairs. The above hair, three-quarters colored, produces a “Smoke” cat. This cat will look blank, until the fir parts and reveals the color underneath. If the cat also has the silver inhibitor, it is a very striking combination.
If the width of the wideband can be changed to over less of the hair. If about half is tinted, the cat is called “shaded”. If only the tips are colored, the cat is called a chinchilla. This is very popular for Persians. The cat looks almost white, with hints of color. But in fact it is genetically black.
Another popular variant of shaded cats are the shaded goldens. These cats have the tipped or shaded color, but do not have the Inhibitor gene. If the cat is bred to have high rufousing like a brown tabby, then the cat will appear to be a golden, almost orange cat with black highlights.
These are all pretty uncommon genes in the general population, which is one of the reasons cat with these traits are pricey. It takes a lot of work to isolate them and adjust them to the right look that will win in the shows.
Note: I’ve put this and some additional genetic information in a separate page for easy reference. I hope you find it useful.