6 yr oldsays he sees colorful and white spots in low light or dark. Should I be concerned?

No, but see a doctor. Go see your pediatrician! Seeing spots like this is probably nothing, but sometimes tumors and neurodegenerative diseases (multiple sclerosis, other rare demyelinating diseases) can cause this.
He should see his Dr. As dr. Wang says, it may be nothing, but it's better to get him evaluated to ensure that there's no underlying problem. Migraines are another potential cause of seeing those spots, even without having a headache.