Sable

Sable is a pattern somewhat similar to grizzle. The pattern constists of a phaeomelanin base with (or without) eumelanin tipping to various degrees. A dog with no or very little tipping is often referred to as clear sable while one with heavier tipping is often called a shaded sable. A clear sable with a mask is referred to as fawn in many breeds.
The gene responsible for sable is found on the A-locus and referred to as ay. It is the most dominant gene on its entire locus, dominant over aw (grizzle), at (tanpoint) and a (recessive black). The dog will however also need kk on the K-locus (allows expression of A-locus pattern).

Some sable breeds, like shetland sheepdogs and collies, have a type of marking on the face, with light colour around the eyes and dark forehead. This is called a widow's peak.
Many sable dogs also exhibit urajiro. This gives them a colouration simimilar to a red grizzle.

Go here to see an example of sable developing from puppy to adult.

A rough collie and a shetland sheepdog, both sable and white. They both also have clearly visible widow's peaks.