No confusion possible since you should hear "est" in the middle.
By the way, it is NOIRE (vache is feminine)
After learning "le chien" and "la chienne". I want to know how to distinguish a male cow and a female cow.
un chien noir (masculine singular) - des chiens noirs (masculine plural)
une vache noire (feminine singular) - des vaches noires (feminine plural)
No, but since you know that "la vache" is feminine, "noire" must be in feminine as well.