If the TOS uniforms were supposed to be green but turned out gold, they should have PAINTED THEM GREENER!
It wasn't always a question of what they
wanted.
Theiss liked to use materials that he thought would look odd and interesting on screen. Early on, he sometimes used materials that turned out to be unsuitable in one way or another - because they didn't turn out to wear well, or didn't appear as he'd hoped on camera, or because they were difficult to maintain.
An early example: the "landing jackets" worn by Pike and company in the pilot episode were constructed of thin leatherette turned inside out so that the grey foam backing showed on the outside. Very cool looking, oddly shimmering effect on camera. Unfortunately, the foam backing snagged and tore easily - every time an actor rubbed against a papier mache bolder it would leave a visible scar on the material. So the jackets were abandoned.
Another example: the first time the production version of the uniforms were cleaned - after a day or so of shooting on "The Corbomite Manuever" - Theiss discovered to his horror that the lovely looking cotton velour shrank very badly. Costumes had to be retailored - hems and sleeves lengthened, zippers torn out and resewed, collars replaced - as quickly as possible during the shooting day. As a result of the quick work, if you look at stills from the episode you'll see the most bizarre mismatched collection of oddly shaped collars and ill-fitting tunics. Some of them seem to change from shot to shot.
Which brings us to your formulation...if it were applied to "The Corbomite Manuever" it might read:
If the TOS uniforms shrank so they looked terrible on camera, they should have stopped and made new ones out of something that didn't shrink!
Which brings us to the real reason it was acceptable to have the uniforms appear differently - more gold, less green - than the producers and designers had planned: the production didn't have the time, didn't have the resources, and didn't have the money to replace that much wardrobe early during the series run. They accepted that the uniforms would look gold, just as they accepted that they'd have to deal with the cotton velour for two entire seasons before the material was replaced.
One last thing: it's absurd for a bunch of
guys to argue over whether a mixed color is green-gold or gold-green or taupe or beige-gold or whatever, because American men are only capable of seeing eight or nine colors. See, in kindergarten we're all issued these crayons, eight to a pack and each about the circumference of a horse's leg. They are: Red, Orange, Yellow, Green, Blue, Purple, Brown and Black. We're thus imprinted, and these are the only colors we'll ever recognize.