Grey

Grey is a gene where white hairs progressively begin to appear on the body as the horse ages, until the horse is almost entirely white, or pure white. A grey horse may go through a heavy dappled stage, or may go white very early on with freckling, known as fleabitten. You may draw your horse at any stage of greying, so long as it is visible somewhere on the body. 

At the minimum, it may cause a grey muzzle and goggles, while at the maximum it may create an entirely white horse. Grey does not affect skin colour, and the skin colour should be appropriate to the horse's base colour. Base coat tends to be fairly desaturated. 

Greying will not flatly desaturate a base coat. It will always display some form of white hairs advancing on the coat, whether this be through dapples, mild roan-like texture, or fleabites. Even on a fairly desaturated coat, warm points may still show around the flank, belly and muzzle.

The geno code for Grey is written as:
nGr or GrGr