When it starts to snow the leaves stay green, you have to quit and reload the world for the leaves to start the transformation from green to the silver colour, also if you go through a portal to the nether then back again the leaves start to revert back to green even tho it’s still snowing,,, again you have to quit and reload the world for them to start the transformation again, I play in the natural texture pack but have tried various others texture packs with the same results,