The first step in the digital coloring process; flat colors! I know some artists who bypass this step and just go straight to painting, but I prefer the separation that flats offer. It gives me the ability to select a specific portion of the drawing to work on. I also try to lay down flats that are similar in tone to the final color of that element, which for some is a no-no. Traditionally, flats are laid down in hues that don't reflect the final colors and are created purely for the purposes of separation. However, I tend to go in and paint in a separate layer above the flats, and I like that my "paint" combines with the flat colors below. I studied traditional painting, and this feels more natural to me; building up layers of color.
It can be an arduous process, and I'm nowhere near as speedy as I would like to be, but I definitely learn something new with every piece I color.