Changing colours and textures in Fortnite Creative?

How do you change the colour and texture of props, grass, particle effects and similar in Fortnite's Creative Mode? I know how to do such things in other games like Garry's Mod where there are tools and menus specifically for that purpose, but I have no idea where to even begin looking in Fortnite. I know there are settings for light colour and fog colour and where those are but not for individual items or terrain. For the longest time I didn't even think it was possible until I accidentally stepped into a portal at the Hub and found myself on an island where there were the torches from the viking castle prefab on the walls with purple fire instead of the normal blue.

So, how do I change the colours and textures of things in Creative? Where are the tools and settings for it hidden? I would really like to make an Autumn island and an Island with the colours of the patches of Alien terrain currently in the game.