Re: Struggling With Colour
I think a lot of on-demand type printing is now done digitally, using PDF files, on machines like Ricoh, or Xerox--- digital printing, rather than press-printing. They "read" RGB color profiles extremely well. Of course you'll want a proof printout to check.
The felt-pen color (or similar) should do well. Even color ink: the fact they fade is not an issue when you're going to scan in the illustration. They were developed to be vibrant.
Can we see a sample of your work? Good luck!