How can i make different leaf colors in the same biome like the seasonal forest from biomes o plenty mod?

Title says it briefly but if you didn't quite get it, i want to add a new biome to the game and that biome's trees has oak leaves and a spruce log. I want to randomize the leaves' colors between red, orange, yellow and regular Minecraft foilage green. However i don't want to add new blocks to the game because i suck at adding leaves to the game for some reason. Can somebody please help? I mean I searched through the entire internet and couldn't find any information.