There is a lot of chunk pieces coloured in that type of scheme around my creative redstone world. It annoys me a lot because I can't repair it using grass anymore since it will transform into the same colour back again. One of the most odd thing is that the chunk use somewhat a gravel/concrete powder textures with a dark colour scheme that can't be seen anywhere in the game. In addition addition, the glitching chunks appears to use grass block that have been layered by top snow. This thing annoys me a lot because it appear every 32 chunks away from each glitching chunks. I found that this glitch appears to be related with light level glitch that has been around since 1.14 and the problem is getting worsen in 1.16(I think someone has reported it).It also happens when I going to fast that chunks is still loading. Also , the block can be changed when i use blocks from the nether. I hope it can be repair anyway sooner. Tested on 3gb ram phone with snapdragon 615 chipset.