A Blue Coin as it appears in Super Mario Sunshine
 Game History
Blue Coins first made an appearance in Super Mario 64 for the Nintendo 64. They look just like a standard Gold Coin but are worth five regular coins each instead of just one when collected. Mario can make them appear by ground pounding a Blue Coin Block. After he does this he will have a limited time to collect them.
Blue Coins reappear and play the same role in the remake of Super Mario 64, Super Mario 64 DS. Again they are worth five regular Gold Coins and can be triggered by pounding a Blue Coin Block.
Blue coins also appear in Super Mario Sunshine released for the Nintendo Gamecube. However in this game Blue Coins play a different role. They can be collected as a secret and are used to purchase a Shine Sprite which are the main collectable of the game. You can buy a Shine Sprite for ten blue coins.
Blue coins also appear in the 2D game for the Nintendo DS New Super Mario Bros. Here Mario or Luigi must jump on a blue P Switch to make several blue coins appear in many different patterns. The blue coins in this game however are worth your standard one coin each. Collecting all of them has nothing to do with progressing through the game.
Blue coins also appear in the next 2D Super Mario Bros. game, New Super Mario Bros. Wii. Here they play the same exact role as in the previous game, Mario must jump onto a blue P Switch to make many blue coins appear. They are worth the standard of one coin in this game as well. The only difference is that the player will hear cheering if all the coins are collected.
Blue Coins are set to return in the upcoming Nintendo 3DS game, New Super Mario Bros. 2.