Leaves on Minecraft are originally gray. If you want snowy leaves like on Minecraft Bedrock Edition, you can find it in Minecraft versions storage: assets > minecraft > textures and search leaves there. They look completely gray except for azalea leaves. By adding more white color, you'll get snowy leaves like on Minecraft Bedrock.

My resource packs are modified and made differently. I don't make these snowy leaves look the same as Bedrock. I modify it by adding more white and blue colors. If you prefer this gray color, just change the textures on this resource pack by replacing the .png you prefer.