Blue Yoshi

Blue Yoshis (also called Dark Blue Yoshis) are a color variation of the Yoshi species.

Super Mario World
In Super Mario World, any Koopa Shell held by a Blue Yoshi will give him the ability to fly; the abilities gained from holding Yellow and Red shells are also granted.

If a Yoshi of any color manages to find Yoshi's Wings, it will turn into a Blue Yoshi and fly up to a bonus stage. After Mario and the now-Blue Yoshi complete the bonus stage, the wings will be lost, though the Blue Yoshi will retain its new coloration.

Additionally, a baby Blue Yoshi can be found in the underwater Star World 2 stage.

In the Game Boy Advance remake, Super Mario Advance 2: Super Mario World, a Yoshi will not change its color upon finding Yoshi's Wings. Also, once the Baby Blue Yoshi from Star World is found, Blue Yoshis can be found in lieu of where Green Yoshis normally are if Cape Mario hits a ? Block containing a Yoshi Egg.

Super Mario 64 DS
In Super Mario 64 DS, the third player in VS. Mode controls a Blue Yoshi. Blue Yoshis don't have any unique ability in the game, as all Yoshis have the same abilities.

New Super Mario Bros. Wii
A Blue Yoshi was set to appear in New Super Mario Bros. Wii, but he was scrapped and then replaced by a Light Blue Yoshi.

New Super Mario Bros. U
Though general Blue Yoshis don't appear in New Super Mario Bros. U, blue-colored Baby Yoshis known as Bubble Baby Yoshis do. They have the ability to spit Bubbles at enemies, turning them into Coins, a Power-Up or a 1-Up Mushroom.

Super Mario Run
Blue Yoshi was made available as a playable character in Super Mario Run following the release of the version 2.0.0 update on March 22, 2017. It can be unlocked after purchasing Blue Yoshi's House from the Kingdom Builder shop for 800 coins, which only becomes available if the player has collected 50 Red Toads and 50 Blue Toads.

Super Mario World 2: Yoshi's Island / Yoshi's Island: Super Mario Advance 3
In Super Mario World 2: Yoshi's Island, a Blue Yoshi is playable on the Castle of every world, except for level 6-8, King Bowser's Castle; in which a Green Yoshi takes his place. This makes Blue Yoshis the least-used of the Yoshis.

Yoshi's Story
A young Blue Yoshi appears as a playable character in Yoshi's Story. His favorite fruit is Grapes.

Yoshi's Woolly World / Poochy & Yoshi's Woolly World
Blue Yoshi appears in Yoshi's Woolly World and Poochy & Yoshi's Woolly World as an unlockable Yoshi design. After defeating Mega Baby Bowser in King Bowser's Castle, the player unlocked various colored Yoshi designs, with Blue Yoshi being amongst them.

Super Smash Bros. series
Blue Yoshis also appear in the Super Smash Bros. series. Although not playable in Super Smash Bros., a Blue Yoshi appears with the Yoshi team in 1-Player Mode. In Super Smash Bros. Melee, Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U, Blue Yoshis appear as a recolor for the regular Yoshi. A Blue Yoshi also represents the blue team in team battles. A Blue Yoshi also appears as a Sticker in the third installment of the series.

Paper Mario series
Blue Yoshis are also present (and live) in the Yoshi's Village on Lavalava Island, featured in the first game of the series. One blue Yoshi is the parent of the blue Yoshi kid of Fearsome 5; the other is the shopkeeper of Yoshi's Cabana.

In the sequel, one of the Yoshi Kid's colors is blue. The Blue Yoshi Kid will be obtained if the amount of time that passes between the point where its egg joins Mario's party atop the hot dog stand to when Mario eventually meets the newborn dinosaur after running from the Armored Harriers is between nine and eleven minutes.

Mario Power Tennis / New Play Control! Mario Power Tennis
In Mario Power Tennis, Yoshi can change colors every time he performs a Rolling Egg Return, provided the player has completed the Flower Cup with any character. One of the colors that Yoshi can turn into is blue.

Mario Tennis Open
Blue Yoshi appears in Mario Tennis Open as an downloadable QR code character. Like Yoshi, Diddy Kong, Baby Mario, and Light-Blue Yoshi, he is a Speed-type character.

Mario Super Sluggers
In Mario Super Sluggers, a Blue Yoshi makes its baseball debut as a color variant for Yoshi. In Challenge Mode, a Blue Yoshi can be found in Yoshi Park. It gives the player several questions in order to figure out the combination for the gate. Afterwards correctly answering the questions, it will join Mario on his quest. The Blue Yoshi has the weakest batting abilities among all Yoshis, but that is compensated by its pitching, where it ranks first among the Yoshis (being tied with the team captain Yoshi).

Mario Sports Mix
A Blue Yoshi also appears in Mario Sports Mix as a non-playable character. It appears in the Dodgeball game, where it assists the blue team on the sidelines. Its red team counterpart is a Red Yoshi.

Mario Kart 8 / Mario Kart 8 Deluxe
In Mario Kart 8, Blue Yoshi appears as an alternate skin for Yoshi. It is available through purchasing both the Legend of Zelda and Animal Crossing DLC packs. In Mario Kart 8 Deluxe, Blue Yoshi is available from the start. Blue Yoshi is the 200cc staff ghost for Super Bell Subway.

Physical appearance
In Super Mario World, Blue Yoshis had dark blue skin, orange gloves, brown shoes, and a brown saddle. For the sequel, Blue Yoshis' look remained almost the same, but the shoes were recolored purple while the saddle was recolored red. The shoes' color was changed again for the Game Boy Advance port, this time to pink.

From Yoshi's Story and on, Blue Yoshis have appeared with magenta shoes and a red saddle. In Yoshi's Island's sequel, Yoshi's Island DS, and Yoshi Touch & Go, the skin tone for Blue Yoshis was darkened.

Notable Blue Yoshis

 * Boshi
 * Yoshi Kid (optional color)

Super Mario Run description
"Yoshi is Mario's loyal adventuring buddy. He can Flutter Jump, and he's got no fear of spikes! Popular with Blue Toads."

Trivia

 * In the SNES version of Yoshi's Island, there is a map error that displays King Bowser's Castle's Yoshi as Blue. This only happens when the level is played for the first time, and resets to green upon resetting the Yoshi's locations.
 * In Super Mario World, upon completing the bonus flying section with Blue Yoshi, the level is immediately completed.