From the Super Mario Wiki
Green Yoshis are the most common colour variant of the Yoshi species.
 Super Mario series
 Super Mario World
Yoshis debuted in Super Mario World, and while yellow, red and blue individuals could be hatched from eggs in the Star World, the Yoshis that Mario found in Dinosaur Land were all green in colour, including the main Yoshi character.
Green Yoshis receive different powers depending on which colour of Koopa shell they are holding in their mouths:
With the Yoshi found, Mario or Luigi can keep the Yoshi to another level.
 Super Mario Sunshine
In Super Mario Sunshine, the Yoshis start out as green but change to a different color once they eat a Fruit upon hatching. They also turn green if they are about to die from not eating another Fruit for a long time, or when they drown in water. While green, Yoshis spit water instead of juice.
 New Super Mario Bros. Wii
Green Yoshis appear in New Super Mario Bros. Wii. They are the first Yoshis to hatch out of Yoshi Eggs when playing the game solo. However, if the player reaches the Flagpole with Yoshi, Mario or other character riding Yoshi will dismount Yoshi. Therefore, only certain levels can be found with Yoshis.
 Super Mario Galaxy 2
 New Super Mario Bros. U
The Green Yoshis are ridable in New Super Mario Bros. U. They behave like New Super Mario Bros. Wii, though unlike New Super Mario Bros. Wii, Green Yoshis are the only colors available. Like in New Super Mario Bros. Wii and Super Mario Galaxy 2, Green Yoshi cannot be taken out of the levels they appear in.
 Yoshi series
 Super Mario World 2: Yoshi's Island / Yoshi's Island: Super Mario Advance 3
In Super Mario World 2: Yoshi's Island, one is playable on every World's first level, and King Bowser's Castle in World 6, although in all other worlds, Blue Yoshi is playable on the final level. Green Yoshi is also playable in every Secret and Extra level in the game. This Yoshi seems to be the character Yoshi.
 Yoshi's Story
 Yoshi's Island DS
Green Yoshis also appear in Yoshi's Island DS. They help Baby Mario and the other babies rescue Baby Luigi. Green Yoshis appear in the first level of each world and in the final level of World 5. In the final boss battle, a Green Yoshi carries Baby Mario.
 Mario Power Tennis
In Mario Power Tennis, Yoshi is playable. Although green is the default color, there is an option to switch colors. Once the player wins the Flower Cup in doubles mode with any character, Yoshi will randomly change his color whenever he performs a Rolling Egg Return. In Mario Tennis Open Yoshis appears as a Yoshi character but is not Green Yoshi.
In Super Mario World, Green Yoshi has green skin, but orange gloves, brown shoes and a brown saddle. In Super Mario World: Super Mario Advance 2, Green Yoshi's gloves were removed to match its current appearance.
In Super Mario World 2: Yoshi's Island, Green Yoshi looks about the same as he does in Super Mario World, but with orange shoes and a red saddle. He also doesn't wear his orange gloves, and instead he has bare green arms. In the Game Boy Advance port, Green Yoshi wore red shoes.
From Yoshi's Story to Super Smash Bros. Melee, Green Yoshi has red shoes and a red saddle. From Super Mario Sunshine and on, Green Yoshi has orange shoes and red saddle, with the exception of Super Mario 64 DS, where his shoes were brown again.
 Notable Green Yoshis
 List of Games
Note that in some of these appearances, Green Yoshi might be indistinguishable from the character Yoshi.