The blues are close enough to be blue on blue, but just far enough apart to "clash. I think a tighter crop to eliminate the bit of hair on the left and upper right would make it a bit more effective.
I like the idea of this shot. I would possibly have cloned the slight white speck in the pupil out. And there is a slight reflection of the photographer in the pupil as well. Just some things I think could have taken this from a good shot to a great shot. Voted 6.
Great idea, composition, and exposure. However, I think both eyes need to be in focus as I find the out of focus eye very distracting. It's possible that it would work with only the near one in focus, but I'm not sure.