Yoshi (Series)

The Yoshi series is often seen as a "spinoff" of the Super Mario series of games—and, much like Mario, it features a multitude of different coins throughout its history.

Super Mario World 2: Yoshi's Island
Yoshi's Island features coins that behave very similar to its predecessor, with one key difference: the inclusion of the all new Red Coins. These coins function similarly to Dragon coins or Ace Coins from the Mario series in that they are a special, less common form of coin that are required for 100% completion of the game. Each level has 20 Red Coins which are then tallied at the end of the level along with Flowers and Stars.

Coins in Yoshi's Island have three states: Interestingly, the "disguised" appearance of Red Coins is actually different in the GBA port of the game, Yoshi's Island: Super Mario Advance 3. In the original, they are nearly always distinctly different from yellow coins with a slight orange hue, whereas in the GBA port, they appear as pure yellow, meaning their disguise can no longer be seen through without the use of a powerup. The reason for all of these pigmental discrepancies is unknown, but perhaps it is to subvert the player's expectations and keep them guessing as to what truly is and isn't a Red Coin.
 * The typical "yellow coin" you'd see in any Mario game, with an extra Yoshi flair embedded on it.
 * An "orange coin", which is actually a Red Coin disguising as a normal coin unless it is a coin dropped from an enemy, which are curiously always orange yet not in disguise and simply behave like regular coins.
 * The Red Coin, usually disguised, but occasionally visible, and able to be seen regardless of disguise with a magnifying glass powerup.

Trivia

 * The coins in Yoshi's Island strongly resemble Dragon Coins from Super Mario World despite having significantly different use. Seeing as how Yoshi's Island is a prequel to Super Mario World, perhaps these are a primitive form of Dragon Coin that have become a rarity in the adult years of Mario's life.