I've seen this bug happen twice before, but the first time, I was in Minecraft 1.18 Optifine meaning I couldn't report that since my game was modded. But now I've seen the bug happen in vanilla 1.19.1, which in this case it took place in a savanna biome. The grass colour of a small row of grass blocks was a slightly darker green colour for seemingly no reason when I first loaded the chunks, and when I changed my Biome Blend from 7x7 down to 5x5, the bug went away. In the screenshot attached, the bug taking place is on the left, and what it should have looked like when I first loaded the chunks (or after I changed my Biome Blend setting) is on the right.

I don't know how common it is that this bug happens, but considering I've seen it twice now, it likely happens decently often during chunk loading and may just not always be noticed.