Snowy Tundra generates grayscale grass with no snow on top.

I generated a buffet Snowy Tundra world, and found this right at the spawn. I created the world several times to see if it was just a onetime fluke, but no. The seed below is the seed with the glitched grass blocks.

-8843279254722522513

Go to the the coordinates in the screencaps, and you'll see them.