Those sound like classic "migraine aura". I used to have migraines, which begin with this visual aura, and now just have the aura.
I think I'd change doctors if they didn't recognize these very familiar visual symptoms, with or without the following headache. These may not be migraine aura, but he is extremely good at describing classic migraine visual aura.
I had the exact same thing when I was around that age but it was more prominent in the dark at night. To this day I have no clue what it is but I can say that I 'grew out of it' by the time I hit puberty. I did read a while ago it could be something to do with spiritual energy, obviously it depends on what your personal beliefs are, but it made sense to me since I used to experience strange things as a child. It never left me impaired in anyway or caused me any physical/ psychological pain. I guess it's something certain individuals may experience at some point.
I had them as well growing up when i lightly prest my eyes they would show color and were more prominent i used to enjoy looking at them just did it now i can still see them i turned out fine i wouldent worry to much about it.
Maybe migraine related? Like an aura.
Are you sure he doesn't have aspergers alot of aspie children and adults see these things. My son has it and they are highly intelligent it's basically a social disorder but they sometimes see patterns and colors. It can be a blessing in many ways!
I experienced something similar after taking accutane. Head feels like static and can see some static if I stare at one spot. Hear static. I finally found the "visual snow" group on facebook and it sounds like your son has visual snow too.
Have you thought as simple as getting his eyes checked? I'm just curious if he is color blind at all. I know he might know the colors by name when you ask him because I've learned that they teach themselves that the color they see is the color we are calling it. If you don't usually ask for the color blindness test they don't give it to them. My son is color blind red, blue, and green. Some clues I noticed was playing ispy, and he'd say a color. Then I'd guess forever until I gave in. Then he'd say it was this, pointing to it. It would be a whole different color than what color he called it. He'd also sit at red lights, and say mom, it's blue. You better go. It's just a thought.
I have had the same thing since i was a child. I still have it and poor vision also. It's called visual snow, look it up on google.
I have something similar. It's called synesthesia. Google it and see if he fits in any of the categories!