I work with Illustrator and ArcGIS all the time, making digital print-quality maps and diagrams for researchers, and sometimes I make advertisements in Photoshop and Illustrator to go in university publications. I also use oil paints and acrylics for landscapes on canvas and the occasional portrait (as you can see in my gallery), some pencil portraits, and the very rare but enjoyable time-wasting effort that are Bryce landscapes.
But... colouring line art digitally? Clearly I have more patience for detailed painting on canvas than using Photoshop for this sort of task. OMG, painful! I have so much respect for artists who can turn a very flat looking piece of line art into a colourful masterpiece that looks like you could either walk into it, or it could walk off the screen towards you. Now that is talent (and again, patience).
... sigh ...
Time to go drag vector lines all over the place. Skill required? Not much.