Oc Doodles

First of all, mad respect for the small canvas. Second of all, let's start!

I guess the lines are pretty nice and neat, though I'd expect that from an artist as expirenced as you. I am quite sad however about your lack of shading. The characters look quite lively, but they just feel too 2D. As regarding colors, 1 and 4 are very pleasant to look at, but 2 and 3 just feel off. Two's purple lines don't match, especially the line's intensity. You should tone the satruation down a bit, and the same for three's eyes too. The colors do not match, the contrast just doesn't work here. Anatomy is pretty good. As of clothing, the characters should have a bit more folds on it (I'm looking at you, number 4). I also really like the little melting effect on 1. And a tip for shading: Try to use one color, with a new layer set with the effect "multiply".

-Sorry if it's lacking, I am very tired.