Pokemon Red is one of the original pokemon GameBoy games. It came out in Japan in 1995 and came out in the US in 1998. Pokemon Red has a pic of Charizard on it, with some pokemon you could only find in this version. The idea behind this was to interact with Blue version using the link-cable. With the use of a link-cable friends could trade or battle pokemon on there game-packs. This is one of the reasons this pair of games are so popular.
Pokemon Blue has a pic of Blastoise a the front of the game pack. There idea was to make a version of pokemon for all of the first three pokemon in there Evolved forms. Umfortunately not all of the versions made it to the US. Hear we have the Red and Blue versions, but in Japan they have the Red, Blue and Green versions. For some reasion they didn't translate Pokemon Green into English. For the Japaniese it's hard to get Pokemon Blue for some odd reason. In Pokemon Blue there are some pokemon that you can only catch on this version. There for you have to trade with one of your friends who has Pokemon Red.