It may not be perfect, but it's definatley a testament to your skill. It looked brown to me in the picture, and brown suits it good here. Have you looked at the brown robot minifigure arms from exo force for the tinier toe of the two? Im sure with the right parts and some trial and error you'l get the feet figured out.
Again, great model - see my comments on tTH3. That Mantis rifle is really good.
This MOC looks very good, Xinlo. I especially like how you managed to make the head work using the pieces you had, as from the comparison pic it looks like something that would be somewhat hard to duplicate.
Adrnin: Thanks. The feet actually have 3 toes - two long ones which I built, and a third tiny one n the side which I recently added along with many other upgrades.
Takal: thanks, I was pretty happy with it, even if it isn't even close to the actual gun. :P
Heat: Yeah, it was difficult coming up with a way to depict the head. I would have liked it to be less round, but oh well. If I ever make another one, I have an idea that may or may not work better. Thanks for your comment.
Just to let you know, I upgraded it last night, adding the third toe, a slightly more solid body, strengthened arms (they don't really look different), and most importantly it's silver now. I'll post pics as soon as I get a nice sunny day.