It looks very nice. I think I'd be better if the hair wasn't so... Separated between the 3 layers. Maybe have them blend more without bold lines separating them

I love the perception feel with the mouth, it looks very nice, although a little blurry... The hair looks well done but it looks a bit random, color-wise. The boldness of the lines and the drastic change of color make it seem like there are ONLY three layers of hair, maybe play with colors until you get a more natural look... But it still is an amazing head how it is and I think you did a fantastic job on it!

After looking closer, (just an idea), remove the top layer of the hair and make the (new) top layer darker?