Just installed Quark to go along Biomes o' Plenty (1.16.3 version) and it's changed all of the custiom BoP terrain colors to something vanilla looking. Fiddling w the Optifine changes the color to something closer to the original, but the grass now looks grossly out of place and it's still not what it's supposed to look like. Help?!

Try disabling the "Greener Grass" module in the Client section of the config.

That did the trick, thanks a lot :D!