Which 牛 breeds come in 純色?

Club breed standards describe 純色 for the 澤西牛和瑞士褐牛.

牛 pattern

純色

One color all over with no pattern or white: self in rabbits, cavies, rats and canaries; a tongue or hoof of one even color.

5 牛 breeds list 純色. It is in a club standard for 2 breeds.

Breed	PDCA	BROWN SWISS USA
澤西牛	符合標準 (“with or without white markings”)	No ruling
瑞士褐牛	符合標準 (“solid brown”)	符合標準 (“solid Brown”)

How 純色 can appear or change over an animal's life.