First form Pikachu
3 starter pokemon
His name might be "Red," but he's from Pokemon Yellow.
Then how is it that I have Venusaur, Blastoise, Charizard, and Pikachu on my team in Red? Hm...
And by G/S/C, breeding exists. So Red could technically have gotten them without permanently getting someone's starter.
They wouldn't have called him "Red" if he was supposed to be from Yellow. That just makes no sense. They would likely have called him "Ash".
Blue is as well, otherwise Blue would have a starter pokemon.
Blue didn't have an Eeveelution either. Theory debunked.
I hate this whole "Red is from Yellow" thing, sorry. I just don't get why having all three starters and a Pikachu makes him from Yellow. The Pikachu part is obvious...he's supposed to be the ultimate trainer, so they are going to give him the MASCOT of the franchise.
Red is supposed to represent Red/Blue/Green, thus they give him all of the starters. Would it really make sense if he only had one? Not to mention people would moan out the wazoo if their favorite starter wasn't in his team. If they made it rival-esque, so he has the opposite type of you, he doesn't represent Red, because Red never had the one strong against Blue. If he has the one bad against you he's not the ultimate trainer.
I think you're over-thinking it. I don't think there's a hidden meaning to him having the Pokemon he does, he's supposed to be the ultimate trainer so they gave him the ultimate Pokemon.