Mexico City Metro Line 6 is one of the twelve metro lines operating in Mexico City, Mexico. Its distinctive color is red. It was the sixth line to be opened.

Mexico City Metro Line 4 is the fourth line of Mexico City Metro. The line color is aqua blue and it runs from north to south of the city crossing the city center by its easternmost area. In 2019 it had a total ridership of 29,013,032 passengers, making it the least used line on the system.