Starting Saturday, the Silver Line will start service out to Reston. Eventually, the line will continue on past Dulles International Airport. (Matt McClain/The Washington Post)

Metro will add a new color to its rainbow of train routes Saturday when the Silver Line opens for business.

The line connects Largo Town Center in Prince George’s County with Wiehle Avenue in Reston. For now, it has five new stations, mostly in the Tysons Corner area. But eventually six more will be added to extend the line to Dulles International Airport and just beyond into Loudoun County. Those stations are scheduled to open in four years.

Metro officials said they expect about 50,000 riders a day on the Silver Line in the first few years of service.

Silver is the first new line since Green opened in 1991. It was not part of the original plan for the Metro system, which began in 1976 with five stations in Washington. As of Saturday, the system will have 91 stations and 117 miles of track.

That may seem big, but not when compared with New York’s subway. That system has 468 stations connected by about 660 miles of track.

The Spring Hill Station is one of four in the Tysons Corner area. (Jahi Chikwendiu/The Washington Post)

Christina Barron