I wanted to make the snowy leaves from that better foliage mod but got told you can't, so I instead cheated using optifine to make a snowy version of the spruce leaves depending on which biome they're in!
I changed the spruce model to have cube_bottom_up as parent, and made 2 new texture for the bottom and top respectively.
This makes it so that the leaf doesn't follow the colormap given by the game, but seeing as spruce doesn't change colour ever, I just made the textures green in the png itself.
As for the snow, I made a ctm that would replace the spruce tiles with snowy ones depending on the biome. I have 3 .properties files: