I have read elsewhere that after the uniform switch to the black with blue-grey shoulders uniform around the time of First Contact, that the uniforms worn during the TNG series could still be seen worn by extras in the background during DS9. It has been suggested on another forum that the TNG series uniforms remained the actual formal starfleet uniform, right up through the end of DS9, and that the uniforms that were seen in Generations and Voyager, were a new form of "working uniform" that starfleet adopted, similar to the U.S. Navy's "Working Blues" uniform. After Voyager was lost, starfleet again changed this new working uniform to the black and blue-grey version that was seen in First Contact and beyond, and that Duty Personnel could choose which version of the starfleet uniform they wore, depending on their preference, or Commanding Officers orders. Does this sound plausible?