change the colour of mass placed tree leaves (or make them transparent)

hey guys

I want to make my mass placed trees (i placed through unity terrain engine...) to change the colour of their leaves...

Maybe make them transparent for winter...?

How would i do that? Can simply atach a script to the tree prefab and place it?

And maybe how to make them transparent...

Thanks for ur help ;) Robert

did you try to modify the tree's material hi i am a chinese