Artists

... but when I have to do complex digital color work, I'll do base colors in Adobe Illustrator, then bring it into PhotoShop for the subtle tonal gradations rendered with the airbrush tool.
Try using a rich sepia tone for your linework and shadows, rather that solid black. And if possible, select a very fine soft-edged stroke for your linework, rather than a hard-edged stroke.
For technical inspiration, check out the work of Arthur Rackham. His line-and-wash work was beautiful. It's analog, of course, but the fundamentals still apply. It is worth noting that Rackham very likely applied his pen-and-ink line on top of the watercolor washes. There doesn't seem to be any residual color obscuring the definition of the linework. To avoid over-painting your lines in PhotoShop, select "DARKEN" when applying color adjacent to your linework. That way, the color will not cover the lines, because the lines are darker.
And any advice offered by Goddessartist is good advice. She knows whereof she speaks!
Persevere, and good luck!

On edit: Having come up as a professional long before the advent of computers, I cheat a little by composing the piece on paper with a pencil, then scanning it into PhotoShop, which I can then bring into Illustrator where I can apply layers over the penciled guide. I'll bounce back and forth between those two apps to make the best use of their respective capabilities.
I'm not familiar with Fresco; I'll have to check that one out. I subscribe to the full creative suite, so it's probably in there somewhere!