In the second term of my second year at school, we learned about color theory. The teacher gave us the freedom to do any art and colors.
The way I do my color is to use the color of the atmosphere.

The first art I made is warm and rich. Purple is a warm color and is also symbolizes wealth. A little hint of red also gives it a devilish vibe. And don't forget the gold that shows off the snobbiness. 

The second art is cool with the color blue. Make it feels like a winter wonderland with the flavor of green. 

The third art gives a weary atmosphere. It is a dark and warm dessert saloon. The colors here are red and orange. 

The fourth art is the same as the third. But the art is mostly red, with the hint of natural green.