A lawyer might be able to make the claim that it would fall under "national origin or ancestry" since, to my knowledge, caste is hereditary and hard to change.
But if so then that makes these kinds of talks all the more important. Because it helps Americans recognize a form of illegal discrimination they would otherwise not recognize.
“Race” is a fuzzy concept but generally distinguishes people of different ethnic origins. Indian castes aren’t different races—low caste and high caste Indians can come from the same ethnic group. It’s more like the European distinction between nobility and commoners. That’s also hereditary, but it doesn’t define different races.
But it certainly seems like caste would be a protected characteristic under California law--"Race, Color, National Origin, or Ancestry" are protected characteristics. Caste seems to obviously fall under ancestry.