I am trying to make some random grass top textures for an old outdated texture pack using optifine(1.14.4) and i have all the old random grass top textures that it already had, but it used an old method, and now i don't know how to make it work with the new way optifine does random textures.

Here are some pictures for context


as you can see the 0.png image, (which is what the texture pack uses for the grass top, and then applies the colormap) just shows up as its greyscale version. now i have never really understood how to make a grass top texture from scratch, i haven't a clue the proper greys to use for it or whatever, im just using the textures that were already in the pack. anyone know a fix?