Good job. I like the last one.
When painting look for planes and where would you put boundary between them. Something like you did on for example day 32. There is well defined structure of the face beacause I can see exactly which surface gets the most light.
The last one has got better colours then previous ones but the planes are too blended and a bit random.
Check out gregpro's paintover to see what I'm talking about - http://www.conceptart.org/forums/showthread.php?t=75768
Keep it up. I can also see some improvement