I don't know if you can do it in all states but one of the things that i have been doing is getting a swatch of the color I want, either by spraying a small square of styrene with what i want or getting a swatch from the paint section at a home store. I can then take that swatch to a professional auto paint store and they have an optical scanner that will match the color near exactly.
They can then put that color, either flat, semi flat or gloss into a spay can, one of the bigger cans like you would see Krylon in, I always get them to do it as flat as possible. The can should have approx 3x the amount of paint as a Tamiya spray can, and costs about $24, which is about the amount of 3 cans.
I think it's worth it for a couple of reasons, in the case of the tie, the Tamiya haze grey is semi flat if i remember right, but i can get a can that is flat, and these come out dead flat. Also it's great to have the can just sitting there always ready to spray, finish a few parts, spray them, go work on other parts while they cure. No need to set up an airbrush for basecoats, these cans have a very fine spray, as good if not better than most hobby spray cans. Lastly, it's good to have a small library of colors, the shop has a file with the colors I get, so if i run out or need it for a similar project I just bring them the paint #.
mike