In the 'olden days', sorry I'm of an age!, keepers were obliged to wear the same colour shots and socks as the rest of their team, it was just the shirt that was a different colour, though nearly always green.
In fact this was the case until relatively recently, maybe 20 or 30 years ago?
They could have done. I think a club is obliged to enter in to an agreement to wear it's third choice kit a set number of times a season.
This question came to the fore two or three seasons ago, when Norwich turned up at the Amex wearing a peculiar claret kit that not even their own fans had...