District Mayor Vince Gray unveiled four possible color schemes for the District's cabs Monday, though it could take nine years to paint all of the city's taxis the same color regardless of which scheme the city chooses.

The D.C. Council voted earlier this year to paint all of the city's privately owned cabs the same color as part of a broader effort to upgrade taxi service.

But current cab drivers won't have to repaint their cars until they upgrade their vehicles -- which most of them don't have to do until 2018. With some drivers eligible to request extensions for cars now in "mint condition," DC Taxicab Commission Chairman Ron Linton said it will probably be 2021 until all the city's cabs are the same color.

"We're trying to make this a process that is not economically onerous for folks," Gray said. "I actually think cab drivers will make more money as a result of this."

Linton said cab drivers have to pay about $1,500 to paint new cabs anyway, so there will be no added cost for the city's color scheme. Linton said almost all new cabs coming from the factory are black and must be repainted.

Residents can see the four color schemes -- two dominated by red, two dominated by yellow and green -- at the Verizon Centerand can leave a their opinion on those they like or hate in the comment box. A total of nine color schemes can be seen at the taxi commission's website, dctaxi.dc.gov. Comments can also be sent via Twitter at #votedctaxi.

Residents get to offer opinions on the colors, but the final decision will be made by the taxicab commission in February, officials said.

"It's just to get a sense from the public on what their views are," Gray said.

The cabs will remain at the Verizon Center until Inauguration week in January, and will then be moved to a tent at Union Station. From there, they will go to the Walter E. Washington Convention Center for the Washington Auto Show in early February.

Gray said he expects the city to select a vendor in two to three months who will supply the smart meters for every D.C. cab, offering credit card payment and GPS navigation.

A vendor selected last month was rejected by a D.C. panel of administrative judges, who said the city employee in charge of awarding the contract did not give enough consideration to competing offers.