I'd say the first, because it has a lot more meaning into it and the colours seem to match nicely (though the overlay of the background image looks a little too sharp when in comparison to the eye which appears to be blurrier. Also the colours are a little contrasted, so if that was downtoned a little, it'd be fine. As for the second one, I'm not even sure what it is, but blue/green/red aren't matching that well and aren't complimenting each other due to the positioning. The third one looks nice - like an optical illusion, but for longevity, I don't think people would enjoy looking at it too often, compared to the first. ~