So we are working on very similar things. Here is a WIP re-working of the NYC subway nomenclature. Line coloring, names, and service labels organized into meaningful patterns.

https://i.imgur.com/UNAT0ZV.png

To fill in some blanks, I am using information channels in a very similar way to your bloom filters. I divide the type of information into the type of visual indicator. Colors are for the broad outline of route, names are for specific route, shapes are for stopping pattern information (express or local). Eg A train going from the Bronx down to Coney Island would have to be in the red-brown palate, its name would be a two digit number with the second digit <5, and depending on if it skips over any segments (indicated dotted lines) it would either have a <> label or a [] label.

I had thought about your "fingerprint" idea. In fact I almost came on it accidentally when outlines of labels in my table changed but the interior didn't. I figured having two colors, a major one for the general palate and then an outline for further specifying, would solve a ton of encoding issues. But ultimately I rejected that idea because I found it too confusing to be able to lookup in either direction (from seeing train to knowing map AND from seeing map to knowing train). It became unclear to me where I should be matching the interior color to a line and where I should be matching the outline color to a line. It was too hard to follow.

The major advantage of colors is that you don't have to mentally trace the whole line on the map to figure out where a service goes. Its very quick to see that the red line which started at X must be the same one you glimpse latter at Y.

To my estimation, you can encode at most 4 bits on colors (1 bit RGB + dark/light), Perhaps 2 bits on shape (circle, triangle, square, diamond), and the rest has to go on to the name. So, reasonably, at a glance your labels can tell people 6 bits of information. Organize it by most significant bit first. If you could only tell me one bit of information about a bus service, which bit would it be? Color that first bit of difference with red / green. Then look for your next bit. For my map, the very first bit was either turns right around 50th St into Queens or keeps going north towards the Bronx. At first I colored everything in these two categories, and when I was done I was left with a handful of lines that all had Broadway Junction in common. Those became the blue pallate in my map. Sometimes, as you start to fill it in, the underlying symmetries of the transit system pop out at you and the amount of complexity seemingly evaporates. A good map should per-generate this insight on behalf of the readers. You are on the right path.

I'd love to talk at length but this is all the length I can afford right now. So here's is my take away message for you.

192 bits is way more bandwidth than you can reasonably hope to communicate in the service label. Look closely at the map of services and figure out the most important 3 or 4 bits, then communicate that. Stick to one color per label, possibly with black or white outlines/fills to encode more information. Be consistent, one type of information gets one type of encoding. A shape is not just an additional color for design purposes.

Edit: I dug up my old comment ranting about my map if you want to read more. https://news.ycombinator.com/item?id=34666190