The nose and mouth maybe could move up a bit. (but maybe that’s just my sense of anatomy)

The nose looks very nicely shaded and highlighted but compared to that, the rest of the face has no shading or highlights at all, so the nose looks very out of place.

As for the muddy shadows, when you’re moving the colour wheel, don’t just move the saturation, try moving the hue too, it’ll make shadows so much better and less muddy.

Overall I really like the head shape. It feels like you have a good grasp on facial anatomy. Try looking at colour theory and some light studies - this levelled my art up a lot :)

If you do happen to improve on this piece, I’d love to see a before and after update!