I like his face already. He's got a ton of character and a slightly quizical smirk in the eye. He might benefit from a little more darklining though, like around his eyes and eyebrows? Just to make his features pop a little more. If you really want to go the extra mile what about a faint glaze of red in the tip of the nose?
I can't put my finger on it, but for some reason I'm not digging the blue yellow green combo... I can see that vibrant colors would be appropriate for a quirky wizard type, but something's off. Maybe if the green was a deeper forest green instead of a shamrock green it would work better for me. I dunno... I can't explain it.
Not sure I like the flesh tone on his glasses... what about trying a streaky pale blue/white combo to make it look more like glass?
I like where you're going with the highlights and shadows on the blue parts. The green could stand to come up a few more levels in the highlights (or down in the shadows) to make it match the value shift of the blue.
You might want to tighten up the transition line between the yellow "lining fabric" of the cloak and the green "outer fabric". The line you have right now is a little blurry. I would also suggest a fine darkline between the two colors, since there would be a natural shadow where two different fabrics are sewn together.
Overall he's coming together quite nicely. Just remember that glazes are your friend. They will help you with your blends and can add subtle areas of color shift for interest.
Keep it comin'!
Jen