looks to me like you just added some highlights and made his cheeks rosy and if your light is coming from behind him the backs of his legs wouldnt have such a dark outline like that same with his back, id say the best improved spot would be his left side of the lower portion on his jacket and the back of his right foot
oh and please fix the out of the lines coloring above his left boot :p we arent 7 years old anymore are we?
a good tip to see how the color, shading and highlights should be is to take a black tshirt of yours, im sure you own some black article of clothing, toss it over the back of a chair and look closely at the values in the cloth, where the shadows and highlights are, the general color of the darkest bits compaired to the lighter and how the color fades into itself, look at it from an angle of light similar to what youre aiming for in the drawing. why do i say color? because your "black" tshirt isnt black unless its a new moon and your lights are off, basically theres SOME, color there, not much but some, but thats a lesson for another day lol