The rainbow sheep was a rainbow variant of the sheep found only in Minecraft Earth.

Rainbow sheep were a rainbow-colored variant of the normal sheep. They had similarities to the sheep name tag easter egg in the base game, but unlike it, the rainbow sheep didn't change colors. Their wool went in a rainbow pattern with the red section being the biggest one and covering the front part of the sheep, orange wool covering its lower front legs, and yellow, green, blue, and violet stripes running along the rest of the body. The wool on their hind legs was violet in color.

https://minecraft.fandom.com/wiki/Minecraft_Earth:Rainbow_Sheep