This gene dilutes the coat color of any color with which is is combined and it is possible to produce Dilute Normals, Dilute Argente, etc. When combined with Platinum it produces the Black Eyed White or Pink Eyed White.
The Umbrous was discovered in the USA in 1998 and is a darkening gene. It does not exist on its own but combined with any color it produces a "sooty" version of the color. The effect of the Umbrous mutation on the normal coloring is to turn the belly from ivory to a sooty gray/brown color and the normal brownish-gray back and sides become darker.
The Umbrous can be combined with any colour to produce a "sooty" variation.