Caps are hats that Mario, Luigi, and Wario can wear in the games. There a total of three hats in the original game - The Wing Cap, the Vanish Cap, and the Metal Cap. Yoshi doesn't have a hat, but he can transfrom into one of the three. Mario's hat is red, Luigi's hat is green, and Wario's hat is yellow.
Info Sign: "There are special Caps in the red, green and blue blocks.
Step on the switches in the hidden courses to activate the Cap Blocks.