One color. Simple and recognizable shape. Proportionally still the size and location of pupils compared to the rest of the eye. Enhances the emotions the face and body is expressing to make the emotional context more clear.
How not to make good eye effects:
Too many colors, or too many details. Improper size (too big) and location make the effect not look like pupils anymore. Doesn’t add anything to the emotion the body and face is making, and instead is used as a substitute for facial and body expression.
Thomas: *inquisitively* I wonder if I have enough money for this. Bank Account: Nope. You barely have enough money to buy food. Thomas: I got it. Bank Account: *distressed* WHY WOULD YOU DO THAT?! Thomas: *barely moving lips* I don’t know.. Bank Account: Aaaaaaaaaaaaaaa Thomas: AAAAAAAAAAAAAAAAAAAAAAAa