Base coat colours
Coat colour dilutions
Genetic disorder tests
Most horses are chestnut, black or bay/brown*. Many other unusual coat colours come about when these basic colours are modified. Just two genes control these basic coat colours.
The extension gene (MC1R) controls the production of red pigment (i.e. to produce the chestnut coat colour) vs black pigment (i.e. to produce black or bay/brown coat colours). If your horse or pony is bay/brown or black, you will need to use genetic testing to determine whether they have one vs two copies of the version of this gene that produces black pigment.
Genetic testing for these genes lets you predict and advertise what colour foals your horse or pony might produce. Read more about chestnut, black and bay/brown and ask questions here...