So what is the big deal about Red and Blue versions? Why don't they just make one game and call it a day? Well there are a couple of reasons why Nintendo decided to make different versions. Let me start out with the basics first then we will get into some of the techno mumbo-jumbo.
The Pokemon series and games started in Japan and spread over to America soon after it was started. The games that were produced in Japan were Pokemon Red & Green. Why we never saw Green was explained in the Pocket Monsters Green section. In America the popular one seemed to be Pokemon Red most likely because of Charizard the fire Pokemon on the cover of the game.
Blue version has a couple differences that make it an easier game to use. For one, the version exclusive Pokemon in Blue do have somewhat of an advantage over the version exclusive Pokemon Red. In that instance Vulpix could be considered better than Growlithe in the games (though I disagree). There is also the Game Corner Pokemon that are cheaper than the Pokemon in the Red version.
The biggest difference between Red and Blue is the version exclusive Pokemon:
The version different Pokemon is pretty much the only reason they made a couple of different games to force you to buy all of them to fill out your Pokedex. If it wasn't a money thing then Nintendo wanted you to be forced to interact with other people with the opposite version with you. Whatever the reason is I hope this article helped you decided what game to get if you were pondering.