On a SEPTA Regional Rail and Rail Transit map, what train line is indicated by the color blue?

The color blue on a SEPTA Regional Rail and Rail Transit map signifies the Market-Frankford Line. This line is one of the primary routes within the SEPTA system, providing critical service along its designated corridor. The Market-Frankford Line, often referred to as the "Blue Line," runs from the Frankford Transportation Center in the northeast to the 69th Street Terminal in Upper Darby, effectively linking various neighborhoods and locations across the city and suburbs. Understanding the mapping system's color coding helps riders quickly identify transit options and navigate the network.