Supraland

As you progress the game towards the blue crystal you'll come to an area (after the holy halo guy) where there is a Red (Doc Brown) standing outside a building, and inside that building are white key cards.. Simply take one of those key cards back into the previous map you came from, drop it on the colour change slab, then head over to where you drop in materials (to change colours) and smack the tree in front of you.. The leaves will fall in turning it Green, the achievement will unlock as soon as it's coloured upon pressing the colour change button.

*there is also an achievement "1337 Hacker" for changing one card to Red as needed to progress.

Credit: RuneSnow