Different colors express different moods, for example we often associate red with anger, blue with sadness. So the color can affect the mood set for you artwork. Also, in like abstract drawings it can help you because we often associate colors with certain landscapes.
Synonyms help us connect unknown words with known words. For example, one may not know the meaning of the word "nefarious" when used in this context: "The offense was more nefarious than previously thought." If we replace "nefarious" with "evil" or "wretched" the meaning is more comprehensible to those who don't know the meaning of "nefarious": The offense was more evil (wretched) than previously thought."
I hope this helps, I used nefarious as a somewhat uncommon term to better illustrate my point, and to explain why we use synonyms to learn new words. Simply put, synonyms bridge us to the unknown using the known as solid ground build from.
The answer would be Catholic Arts are mostly base their arts in the bible and about their religion while the Protestant art rejected mostly of the arts from catholic arts and create a simpler and new way of arts. They depict it because they want to be different from the catholic and its also because of the reformation.
