Hebetes
Hebetes is base coat modifier that causes the coat color and any markings to be dulled, or completely de-saturated. A cat with Hebetes will take its color from the usual tan / cream / agouti / mutation swatches, but must be at least slightly de-saturated (i.e. closer to grey.)
If a cat has hebetes, its coat must be at least 30 lower in saturation value than the normal swatch, and can be desaturated at any point below, including fully.