Blue

Kanto (LeafGreen)
Blue collects his first Pokémon, which he chooses to be a Squirtle, from Professor Oak the same time as Red. Blue initiates a Pokémon battle with Red immediatly, and comes out on top, gloating as he leaves Professor Oaks lab and Pallet Town on his journey to become a Pokémon master.

At some point, Blue catches a Pidgey (which evolves into a Pidgeotto), a Rattata and an Abra, to complete his four man rooster. He challenges Red to a battle in Cerulean City, but is defeated solely by Red's Charmeleon. Blue storms off to continue training his Pokémon.

Blue and Red would again meet on the S.S Anne, just as Blue has aquired the HM Cut from the captain. He again forces Red to battle once more, where his obvious attempts to train his Pokémon to better Red become apparant. His Abra has evolved into a Kadabra, his Rattata has evolved into a Raticate and his Squirtle has now become a Wartortle. Despite his efforts however, he is again defeated by Red.

At some point, Blue caught an Exeggcute and a Growlithe and added them to his team, at the same time removing Raticate, and storing him in his PC. Blue, intent on beating Red to a full Pokédex, travelled to Lavender Town to try and catch a Cubone from Pokémon Tower. He was unsuccessful, and once again met Red. Blue battled Red with his improved team, but still lost as Red had reinforced his starting six with a Dratini.

Blue continued to improve his team thereafter and forced Red to battle him in the Team Rocket controlled Silph Co tower, seemingly not caring about the other hostages, only proving to Red that his Pokémon were stronger than his, and he was a better trainer. The battle was close, with Red however managing to narrowly win. It was from this battle that Blue vowed to take on the Pokémon League and become the Champion before Red. Blue then left Red to deal with Team Rocket at Silph Co alone.

The journey of how Blue then becaming the Pokémon League Champion, remains largely unknown. It is however clear that he was only just crowned as Champion when Red emerged to challenge and the defeat Blue. It became clear to Blue that the way he was training his Pokémon was the reason for his lost. He vowed to become a better trainer and returned to Pallet Town.

Sevii Islands (LeafGreen)
Blue is given a National Pokédex by Professor Oak, along with Red, and he immediatley heads to the Sevii Islands in order to capture and collect new data on Pokémon. He briefly encounters Red on Fourth Island, informing him that Lorelei is there, before he disappeares off again.

Appearence
Blue has spikey light brown to dark blonde hair. He usually sports a black shirt and sometimes a brown jacket.

Personality
Blue used to have the typical personality of that of an arrogant and spoilt individual. He took every opportunity to belittle and humliate Red on their meetings, despite the fact that Red often got the best of Blue, eventually defeating him to become the Pokémon League champion.

After his loss to Red, and the title of Pokémon League Champion, Blue soon realised the error of his ways. He vowed to train his Pokémon better and treat them with more respect aswell as not overestimating his own abilities. How long this new attitude will remain is still to be seen.