Colored Grass Issue

This occured in my iPhone 5s.
I have encountered a bug while I was playing Minecraft Bedrock Edition. Somehow I saw colored grass in a certain location (I think it was in a chunk). I saw black, purple, cyan, etc. grass and it had a snowy texture on its side when there is no snow above. When I restarted, it came back to normal. What’s happening? Although this screenshot has only black and green, there were many colors.