Minecraft wiki entry for Data_variants, associated text: Some blocks appear tinted by biome if their normal variants usually would be. As leaves were tinted as per their numerical data values, setting the number prior to destroy to 1 for specifically potted leaves causes them to be tinted with the spruce color, and setting it to 2 gives the birch color. 0 or 3 results in them being tinted per biome like oak and jungle leaves are.