This is a minor glitch where patches of grass will randomly turn a different color on the top while being random biome-specific grass on the sides, despite being a superflat world (meaning only plains grass). I do not know how to reproduce it, as this patch of grass was in a section of the world I hadn't built on or anything.  My guess is that it might have something to do with night vision, as I had a night vision effect wear off a few minutes earlier. The issue was fixed by reloading the world.

As for the world itself, it is a small world (2 MB max) with cheats on and no texture packs ever being enabled on it. No expirements are on, either.

The video displays the glitch with both the top and side textures.L88EDeImvoNIBOFz.mp4