In Super Mario Run you can collect different colored (Red, Purple, Blue, Yellow and Green) Toads in Toad Rally. These Toads can be used to unlock buildings, decorations and even additional characters, such as Yoshi. You earn Toads by performing different jumps during Toad Rally matches. Different colored Toads appear on different stages, which you can unlock by completing the 6 different worlds in the World Tour section. You can see what colored Toads will appear before each match in the "Expected Crowd" section.
How do I get different color Toads in Super Mario Run?