BART alone was confusing before they made the trains actually match with the colors on the map, circa 2016. Used to insist on only designating trains by endpoint, except the endpoints changed as they expanded lines, and also changed depending on the day/time. So even a year into daily riding BART to/from work, I took the wrong train a few times.

I went to NYC and also various other countries, easily understood the train/subway system even if it was in a language I don't understand. Except for Italy.