One of the most important things, to me, when designing a background or scene is getting the colours right, I’m incredibly picky about it! It helps me pinpoint an exact mood or atmosphere.
I used to be very timid with colour, and only drew things in black and white. Now, it’s my favorite part and I get really excited seeing colours blending and forming new ones. Mixing colours is very different when you are painting in Photoshop though, it’s more of a layering process, with access to a huge spectrum of options.