Have you heard of Auras? they are different colors of energy that are put out by people and things. Some pople are able to see these and most people are not. I would do a litle study on auras before you haul him off to a Doctor who will send him to a psych.
I would take him to an eye doctor or atleast call them. Kids are amazing and they describe what is happening. Maybe nothing at all (they can be imaginative and creative also. lol!) but I'd check.
i think he is just playing maybe he seen a cartoon with x ray vision and now he wants to pretend he has it too? i wouldnt worry too much kids are funny like that.