Hello!
Coloring is a verb, but this sentence is showing that Andrew enjoys SOMETHING, or a specific noun. In this case, we can use a gerund, which is a verb written as a noun.
For example, Joseph loves swimming.
In this example, swimming is the gerund. Swimming is a verb, but is written in the sentence as a noun.
So therefore, our answer would be A) Gerund.
I hope this helps!