Given to Blue as a Charmander by Professor Oak, however it was not his first Pokémon as he already had a Scyther.
Charmander
Professor Oak gave Blue a Charmander as a starter Pokémon but since Blue already had a Scyther, Charmander wasn't Blue's first Pokémon.
Charmeleon
Blue's Charmander evolves into a Charmeleon at some point before the "Onix Is On!" round in the manga. Blue apparently battled against Brock with Charmeleon and won the Boulder Badge.
Charizard
Charmeleon evolved into a Charizard and again his evolution wasn't shown in the manga. He evolved at some point before "Kalling Kadabra". Alongside Red's Saur (a Venasaur) and Green's Blasty (a Blastoise) Charizard took down "Zapmolcuno", a fusion of the legendary birds Zapdos, Moltres and Articuno created by Team Rocket.