Take a look at this identification parade. These are symbols of the six basic human facial expressions: Sadness, Joy, Anger, Fear, Disgust, Surprise.
Of course, colour adds extra feeling and helps to identify the emotions. Without it you can see below that each face contains only the features that most express the emotion it represents. Or rather, that I feel most express it.
If you don’t agree with my doodles, good. That means you will reach for a bit of paper, or your tablet or phone and start drawing faces and expressions yourself.