On to the colors!
It’s not necessary to have a lot of different colors, in fact it’s much easier to work with a limited palette. For the most part, I will only use these six colors, as well as black for deep shadows and white for some special effects.

Sometimes it may be good to add additional colors to accentuate specific elements. Just remember that less is usually more, since fewer colors make the whole image more homogenous, while many different colors can literally make it difficult to look at.