Eheh, the greenies you added are not highlighted because They are shadowed. They can't be highlighted if there's no other light source. at least 80% of that what you "Greened" isn't possible to be highlighted (Look at it a while... you'll get what I mean). The right leg (His right leg) Isn't shaded yet the way it should be, I'll get to shade it later.
The blue parts at the back actually aren't like you drew them. Here's a real render which I based this drawing on.
The pic Actually after taking a look onto the in-game one, it's like you said. I'll not edit it though, too lazy =)
I agree with the gun; It really needs to be bigger, and I'll make it bigger.
I'll fix that leg as well.
I'll not edit the helmet, It looks perfect the way it is (For me). it is not from the same angle as your one. You should understand that this is a real drawing on a real piece of paper, this is not that easy to correct. I'll maybe try to Warp the yellow parts a little.
The stance just came to my mind ^^
Oh, and I "Denied" your comment (Call it like that) because this isn't supposed to be realistic. It wasn't intended to be drawn "realistic", it was comic-book style. And they are supposed to be drawn simple. The coloring finishes the job, but until i get a tablet, I can't do some intense coloring and shading.
I hope you don't get this comment the wrong way ^^ but yes, it has some flaws here and there and I'll try to make'em better.