The color palette you chose looks good. The hair details and the head gear is pretty incredible. I can't really give advice since the work surpasses my own.
I'm sure you are right ^^; - It is probably the ones I used for anti aliasing though.
But some colors do look too similar I guess. I'm still not sure how to find more interesting color combinations.
There are a lot of unnecessary colours in it, there is 33 colors and there are nearly 7 colors that are used less than 3%, I dont know that much but I thought that might help 
nice!