What is the predicate nominative and the predicate adjective of , The colt is frisky.
Let's review the difference.
This man is ___________.
If the blank is a noun (this man is a doctor; this man is my father), then it's a predicate nominative.
If the blank is an adjective (this man is tall; this man is angry), then it's a predicate adjective.
So, going back to your sentence: The colt is frisky
Is the underlined word a noun or an adjective?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.