From StrategyWiki, the free strategy guide and walkthrough wiki

There are seven fruits in all which includes apples, bananas, watermelons, grapes, melons, peppers and heart fruits. Each Yoshi has a favorite fruit that gives them more health and points when eaten. Green Yoshi likes watermelons, Red Yoshi likes apples, Blue Yoshi likes grapes, Yellow Yoshi likes bananas, Pink Yoshi likes apples, Light Blue Yoshi likes grapes, Black Yoshi likes all fruits, White Yoshi likes all fruits and all Yoshis like melons. All Yoshis except for Black and White hate peppers and suffer from eating them. The Heart Fruit makes Yoshi super happy, invincible, increases the length of his tongue and gives him infinite eggs for a limiteed amount of time. Also, White and Black Yoshis can hover farther when using the hover jump technique while super happy.