Merle is a colour combination in dogs’ coats. It is a combination of bluish or reddish gray hairs with base hairs in a different colour and (usually) black hairs, which gives a mottled or uneven speckled effect.
Merle is a distinguishing marking of several herding breeds, particularly the Australian Shepherd, and appears in other herding breeds such as the Shetland Sheepdog, various Collies, and occasionally the Welsh Corgi (Cardigan).
A similar speckling in horses is called roan.
