What determines whether an animal produces white meat or red meat?

What about mutton and lamb? I’d say red.

Yes, lamb and mutton are definitely red meat.

All meat from livestock is considered “red meat” by USDA. Pork, veal, and “dark meat” from poultry all contain roughly the same amount of myoglobin; this is about half what is found in beef, and several times what is found in poultry “white meat.”

From Cecil about 12 years ago
And my related staff reportfrom about 10 years ago