If that was the preferred uniform of the rebels, then Leia rebutting Vaders claim at the beginning of ANH was pretty silly, seeing as that there were dead rebel troops laying about and others being taken into custody.
It doesn’t matter if they’re wearing a rebel uniform or not. The fact that they defended themselves against the stormtroopers at all makes them rebels. If Leia wasn’t lying, they would have let the Imperials board peacefully. Her lie was obvious to everyone there. It was done, like the rebel soldiers defending, to buy time for the plans to escape.