Optifine is a key ingredient for my Seasons Texture Pack to working properly, as there are custom colors that work via from the optifine folder within. Birch trees, Spruce trees, Lily pads and few more blocks/plants all use tints that are hardcoded into the game, and optifine/mcpatcher allows the ability to override hardcoded tints from these blocks allowing me to give them the proper colors such as the white for winter.