It looks great, and uses the limited colour scheme really well!
I did notice a slight oversight though, on the left sprite you forgot to make the interior of the cape grey. (It could be an intentional design choice, but I don’t think it is.)
Damn this so cool, you have made really great job with designing this cape. How others already said I’m real fan of it being that simple and colour scheme.
I don’t know if you heard about it but Jake said that there will be soon new contest about back items, if capes would be allowed I think that you should participate in it with this awesome cape but that depends on you.