so, I first drew the base of the eye, then i made the colors go from darkest to lights (its easy). Then, yknow the colors that are in between white and black? Yeah, you'll need those. so first start with the lightest, then make lines (liek how i did) going from around the eye (dont make them too long!). then do it over and over again with the other colors until it'll look like mine! if their isn't enough colors (what i mean is if you already used all the colors that are inbetween white and black) then just press on the darkest gray and make it slightly darker like how i did! and there you go, the final product!

also make sure you make the backround black