Spokesman Mark Hannan said only that the decision would be based on international best practice "around safety and the best visibility for the public."
Although street signs in the former Auckland City have blue backgrounds and white lettering, Papakura and Franklin were the only other "legacy" councils also to use that colour scheme.
Mr Hannan said about 63 per cent of the region's 132,000 signs had a green background.
Although the goal was for all the Super City to have the same colours, that would take several years to achieve as signs would be replaced only for normal maintenance.
That was because the full replacement cost, at $180 a sign, would amount to more than $23 million.
Until next year's call, damaged or worn-out signs would be replaced with those of the same colour.
Orakei Local Board chairwoman Desley Simpson, whose boundary with the Maungakiekie-Tamaki board is along West Tamaki Rd, was surprised signs were not colour-co-ordinated across the region during Auckland Council's first term.
"It's part of the transitioning - I'm surprised Auckland Transport did not make a regional decision pretty early on," she said.
She said her board would have an expectation of being consulted and, although her personal preference was for keeping the signs blue, she would be guided by professional advice and public opinion.
Her board's transport spokesman, Ken Baguley, said he preferred blue as Auckland's traditional colour in pursuits such as rugby and netball.