Maybe is not easy to see (I hope) but I quite hate digital colouring and I'm recently adapting myself to find a less annoying way to do it. I've searched for a tecnique that could at least resembe to me the watercolour tecnique I use handpainting (which instead is a tecnique I deeply love). Not that I colour like digital watercolor, but actually having the non-annoying feel to colour digital. (Hope I'm expressing what I mean... sometime is hard for me to explain how I draw bc is more a feel than a method :/ and my poorly english doesn't help XD)

I'll use the short I'm preparing for Starscream's past as example (since ink is ready).

So here above we'll have two places, both settled in the Crystal City, which we expected to be inside and an aseptic lab, white- light blue mood. So I do some research and got some ideas of how the lights and the colours could be for my Crystal City.

Sometimes I took screenshot from TFPrime backgrounds [or I find some CC0 (a non copywrighted image)] and pick up colours or slap them behind and blurr them so much that the original image disappear and I only have colours left to get the idea of the mood of the panel. I choose this one as reference.

I must say that I usually start with a very dark background to have high contrast with lights and colours, so I don't actually colour the entire figure with flat colours and then add shadows, but more I only draw colours where lights are and smudge it. The difficult here for me is that is not the very dark Autobot's HQ, but a bright lab, so let's see what I can do:

Now that I have one of this "mood" background, I can duplicate e modify on the other panels and add dark and light whenever I want.

Sooo I duplicate the 3rd panel bg and copypaste on other layes, then rotate, modify to create an irregular pattern. I'm also starting searching more some lab lights and I add an overlay layer with a very bright light blu light (very scientific, very autobot). Now let's concentrate on the first panel to understand how light works:

I added more gray\blu dark colours in the background level to start making my character detach from the background itself. Starscream, in the foreground, has the light behind him, so most of the light will only be some hints of hard and birgh light on the borders. The other robot, instead, is more under the light and will have most of his face lighted up. I coloured the idea of where lights will go drawing roughly with high contrast colour here below.

So, I'll start put some colours remembering where the lights come from.

Then i Smudge

And star adding light (usually white on this level) and keep detailing pieces and volumes: if you usually put a little lines of light behind the source of light this will help to make the volume of the subjects more clear and defined. But as you can see, most of the work is done by the original "mood background" color given at the beginning!

I'll cut a little shorter, but let's say that when I want some "WOW" effect, like the lights in the eyes or shiny points of lights, I add a overlay level (above the INK\Pencils layer\s) in which I put all the glowing things I want. This glowing level works better if it gots another color under and dark surrounding colours (Also contrast between two complementary colours exalted this tecnique, but is not our case here). Here used the light blue light of the ambient and the yellow of Star's eye.

So the light blue glowing for the ambient in the end doesn't convince me and I decided to give back the "White-steryl" mood I was searching at the beginning. So I did another level for the Background and give back a tons of white, but still using the blending tool to create some pattern and not a block of white: