Thoroughbred colors part 2

Roan does not exist

*The Catch A Bird Exception: The only exception to the statement that there are no true, dark-headed roan TBs has cropped up very recently. In 1982, a very unusually marked Thoroughbred was born in Australia named Catch A Bird. He looks like a bay horse with white brindling, the opposite of the dark lines seen on "normal" brindles. Stranger still, as a stallion, Catch A Bird has produced four offspring that appear to be true, dark-headed roans, indicating that Catch A Bird carries a one-time genetic mutation that has produced roan. As far as I know, none of the 4 "roan" foals, Odd Colours (1992 mare), Slip Catch (1993 mare), Goldhill Park (1994 horse), and Red Noble (1996 gelding), have been tested to see if they carry the roan gene, but they certainly exhibit the typical roan phenotype. Interestingly, Slip Catch has produced two roan foals, Lavender Fields and Pink Flloyd.Slip Catch and her foals were rescued by Winning Colors Farm in Australia where their rare color is being preserved and promoted. 

Pictured is Catch A Bird, who looks like a brindle, except with white striping instead of dark striping. With regular brindles, the dark stripes are caused by the sooty hairs in the coat being arranged into lines, rather than being randomly scattered. Catch A Bird's color was most likely the result of skewed rabicano caused by a one-time mutation. Because CAB's color was the result of a mutation, it was not hereditable. But because of the close genetic relationship of several white patterns, including rabicano and roan, the mutation manifested itself in the ability to pass on a variation of roan to his offspring which has proved hereritable.

Long story short, true roan is a new mutation in the Thoroughbred gene pool

Slip catch as a foal

Odd Colours as a foal. Notice her dark head and points, typical of a true roan.

Grey

Young

Mid age

Old

Some greys retain odd patches of color known as "bloody shoulder marks" though the marks can occur on the neck, barrel, and elsewhere as well.  Pictured below (top) is Colorful Tour winning the 2003 Essex Stakes. He is a chestnutrabicano, a pattern that is often confused with true dark-headed roan. The rabicano gene, however, is entirely seperate from the roan gene, though it does create a pattern of white hairs that is similar to roan. It is usually manifested as a sprinkling of white hairs radiating out from the horses flank. Rabicanos also have a white-topped tail, known as a coon tail or skunk tail. Other notable rabicano TBs are Cox's Ridge, his dam Our Martha, and Carrier Pigeon. There is some thought that rabicano may be tied to the sabino gene.

Colorful Tour, exhibiting the rabicano pattern. Note the white hairs on his flank and the top of his tail.

This is Skunktail, a bay rabicano, showing off a bold skunk tail that earned him his name. Not all rabicanos have this much white on their tails. He appears to be a sabino as well.