acquired, meaning the eye(s) changed over time most likely due to an inflammatory condition or an injury
There are three variations of hereditary heterochromia in dogs:
Complete, also known as heterochromia irides (one eye is a completely different color than the other eye)
Sectoral (part of the dog’s iris is one color and the rest of that eye is a different color)
Central (different colors within the iris give a spiked or haloed appearance)
Heterochromia is a benign condition though dogs with lighter eye colors may squint more in direct sunlight. The condition doesn't affect vision or health, with the exception of Dalmatians where blue eyes are associated with a higher risk of deafness. Heterochromia is possible in any dog, purebred or mixed. It should not be a trait focused on in a breeding program; this will increase inbreeding and doesn't maintain the breed standard.