CHICAGO (CBS) — Wednesday is red-letter day at the CTA – 25 years since the CTA first began using color-coded route names on the ‘L.’

It’s as simple as black and white: the ‘L’ is part of the fabric of Chicago. However, it’s only been coloring our world for 25 years. The old maps of the city’s ‘L’ system show a complex web of lines and routes.

“We switched to colors to make the system a little more user-friendly,” said Graham Garfield, the CTA’s historian. “They had names — mostly geographical names like Ravenswood Milwaukee.”

CTA was by no means the first big-city system to color code its transit lines. Boston did it in 1965. Transit historian Graham Garfield said colors began to appear on CTA maps in the ’70s, but were not used to identify the lines, which still bore names such as Howard-Englewood, Congress-Milwaukee, Ravenswood and Lake-Dan Ryan.

Garfield said CTA settled on today’s colors in the early 1990s. Orange, which was originally assigned to the Skokie Swift, moved to the then-new Midway line, while the Swift turned Yellow.

Likewise, he said, the Evanston line was not originally Purple, but said Northwestern’s purple-clad Wildcats helped influence that decision.

The move to color-coding was prompted in part by the 1993 decision to change the linking of two major lines, today’s Red and Green Lines.

“The Red Line is our heaviest ridership line, it’s our North/South trunk line, so we wanted to give it the strongest color,” Garfield said.

The Pink Line, debuted in 2006, was named in a student essay competition.

“I believe the student wrote that it was a happy color and made her feel good,” Garfield recalled.

Many long-time riders still use the old route names. For that reason, and for those who are colorblind, Garfield said, CTA always tries to identify by both color and destination.

Eight colors of the rainbow currently crisscross Chicago, but could there be more coming ’round the bend?

“If we add a ninth route, we’re going to have to dig deep into the Crayola box to come up with a new color,” Garfield joked.

Odds are that the next line, if/when it occurs, will be silver — the runner-up to Pink in 2006.

25 years ago, it cost $1.50 to hop aboard — in tokens.