Select the Colors Database located in the Assets/Project Files/Data/ColorsSystem folder.
Click the + button to add a new color preset
Unfold the new element and modify the colors
You can modify existing elements or delete them using the - button at the very bottom of the list.
To change the sky color: select Main Camera object on the Hierarchy window, find Camera script, Environment -> Background, change the color
To change the color of the water: select Water Material located in the Assets/Project Files/Game/Materials folder and modify the first 3 color fields.
