Green hair looks the shadiest to me. Characters with closed eyes are usually made out to be pretty shady. The one at the back had more of a wild feel to him IMHO. Which the tan one with the pony tail doesn't really have. he just looks very calm and calculated...
Like moto said, I also thought he just looked angry rather than shady. Rather, "stern" might be a better way to put it. I think the 2nd (pony tail and tan) was described that way. I don't know if I'm recalling this right, but I don't think he was ever described as wild. He was quite a contrast to his father as I recall.