Thanks for the feedback, folks!
HipGnosis: thanks for your input and for posting that note about not using free software to sell things. I hadn't even thought about that, so I'm glad you mentioned it. Are you doing any sort of patenting for your prototype? Are you worried about someone copying your idea?
There is a local Makers Lab with a 3D printer, but they don't have color. The multi-colored part of my idea seems to be the crux of the issue!
I spent a lot of time today calling various 3D printing companies, and it seems like printing in multiple colors is still very cutting edge for the industry. The only pseudo-affordable multi-color option is gypsum based printing (also called "sandstone" on a lot of sites). It's actually pretty incredible to watch some Youtube videos of this (2 minute one here:
https://www.youtube.com/watch?v=ft_MuAbUHs0). But it sounds like the end result is really brittle and fragile and best for just making things that won't really be handled. From what I've seen, there is a new technology out there than can do multi-color plastics, but it is astronomically expensive (I had a quote for $400 per cubic inch).
At any rate, it seems like the only way to get a sturdy final product that doens't cost a fortune is to do "regular" 3D printing in one color, like you have all mentioned, and then to paint it myself. Now whether I can paint what i need to and have the final product actually look professional is the question!