When I was younger, someone told me that sorrels have the lighter manes (usually with some white hairs interspersed) and chestnuts had same color or darker. I whole heartedly believed this until I got into genetics.
In genetic terms ee is chestnut (if there are no other color factors modifying it), regardless of breed. Sorrel is used by many registries as well as horse owners as a coat color, but it is not a genetic color term. Most horse color information will use them interchangeably.
I would also beg to differ on Chestnut being the most common color. A horse is only Chestnut if it has no other colors modifying it (a palomino is not a chestnut, although it is homozygous for red "ee"). As red is recessive, genetically speaking, you would have more horses black based than red based, and once you take out any creme or grey modifiers, I wouldn't think Chestnut would stand as most common horse color (though it is more common in certain breeds than others). When I lived in Ireland, chestnuts were very rare and valuable, and the Andalusian breed would have wiped out chestnut if it hadn't survived hiding under grey modifiers. Not to mention Friesians, Shires, and Clydesdales (all of which do have the red gene, but very uncommon).
Last edited by Southern Grace; 09-06-2013 at 04:21 PM.