Hi James,
I like your shots. At least you've got the head-room, etc sorted out. However, they are all head and head/shoulder shots. Shoot more and experiment with different angles and bg. Observe how the masters do it. For color and saturation, you must look up Jia Wang. He's got fantastic skin tones and colors, I feel. For composition, look up Will03, our most celebrated portraits and poses photog. Eventually, you will find your own style that you are happy with.
All the best. Keep SHOOTING!! :thumbsup: