The bug

Most types of leaves follow the foliage.png colormap texture. However, birch leaves and spruce leaves do not (MC-3930). Unexpectedly, in Java Edition, they do not have dedicated colormap textures of their own, and the color appears to be hardcoded. However, colormap textures for these blocks do, in fact, exist in Bedrock Edition, making this a parity issue.

These colormaps appear to have been added in the Nether Update, making this a valid parity issue.

How to fix

Instead of hardcoding the colours for birch and spruce leaves, introduce dedicated colormap textures for these blocks and make them use these instead. Attached are the files directly from Bedrock Edition, alongside versions of them with all unused pixels removed (MC-276842).