Nice colourings! Hm... I suppose the only thing I can say you can improve on is to make the shading a little darker to make it stand out more. And perhaps add a slight shadow to the edges of the eyeballs to make them more round-ish. Apart from that, you're off to a very promising start! Keep up the good work!
i agree with what raine aldready wrote, but i'll one more thing:
when coloring eyes, and especially close-up, its a good idea to color the eye whites as well. try a really bright grey color, and then use a slightly darker grey color to make a shade below the upper eyelid and around the iris. it makes the eye come alive a lot more, as (if you look at it) the eye white isnt really white. well, just a tip, and there are lots of ways to do this... ^^