Where can you find pokemon that can learn flash in Pokemon Blue?

Answer 1

Volbeat is the only Pokemon that learns Flash (at level 1) without a TM. Otherwise you have to buy TM 70 (on Diamond and Pearl) or if your playing a different game its HM 05

Countless Pokemon can learn flash, you can purchase Flash from the department store in Veilstone City.
Go through diglets cave by Vermilion city then go down through the trees you need to cut then in the gatehouse talk to the aide (you need to have 10 Pokemon on your pokedex)

Answer 2

The Pokémon that can learn Flash are Volbeat, Bulbasaur, Butterfree, Beedrill, Pichu, Pikachu, Cleffa, Clefairy, Igglybuff, Jigglypuff, Oddish, Paras, Venonat, Meowth, Psyduck, Abra, Bellsprout, Slowpoke, Magnemite, Drowzee, Voltorb, Exeggcute, Koffing, Chansey, Tangela, Staryu, Mr. Mime, Jynx, Electabuzz, Jolteon, Porygon, Zapdos, Mewtwo, Mew, Chikorita, Meganium, Bayleef, Spinarak, Ariados, Lanturn, Togepi, Natu, Ampharos, Mareep, Skiploom, Bellossom, Gloom, Vileplume, Clefable, Wigglytuff, Parasect, Venomoth, Persian, Golduck, Alakazam, Kadabra, Victreebel, Weepinbell, Magneton, Hypno, Electrode, Exeggutor, Weezing, Starmie, Yanma, Wooper, Sunflora,, Sunkern, Umbreon, Espeon, Skarmory, Misdreavus, Elekid, Smoochum, Raikou, Blissey, Entei, Lugia, Ho-Oh, Celebi, Treecko, Beautifly, Dustox, Lotad, Ludicolo, Shiftry, Nuzleaf, Gardevoir, Masquerain, Breloom, Nincada, Delcatty, Medicham, Plusle, Minun, Illumise, Roselia, Spoink, Cacturne, Lunatone, Solrock, Claydol, Cradily, Shuppet, Absol, Metang and Metagross.

Answer 3

Oddish, Abra, Pikachu and a few others can use flash in that game. Just check your pokedex for those three. They are fairly common on the game.

Answer 4

I think any normal type Pokemon can.