5 year old son has had a cold a couple days. Now his eyes r very red. No drainage or itch. Just very red. Why is this?

Conjunctivitis . This sounds like a viral-associated conjunctivitis. This is contagious to others, so precautions should be instituted, like hand washing, avoid contact with other people until symptoms go away, protection of the other eye by not touching, may use warm wash cloth to clean eyelids, ocular decongestants, tears, tylenol, (acetaminophen) fluids, and rest. If gets worse, see an eye md.