This is definitely one of the most processed photos I've seen in this challenge. The composition is good. I would have liked to have seen the boy a little lighter so that you could see some detail in him. The background really doesn't do it for me, but everyone has their own taste.
The kiddo looks a little freaked out or laughing, which im not sure helps or hinders this image. The rainbow effect I don't really care for, it looks alright, but just doesn't do it for me. This image is very odd. I think the large tans/sand distract from the brights and throws this image off balance for me.
There's something so down-to-earth and sympathetic about your protagonist that I enjoy seeing her in this rainbow world. The reflection is wrong but that just kind of adds to the funk. And I want the funk!