This is not an end-all and be-all answer for the later years, but I did want to add that the part numbers for gold snowflakes in 1977 and 1979 are the same, 10010054. So that answers the question indirectly of what color these wheels should be in 1979.
FWIW I've never seen any indication the color was ever changed, just based on looks, but I also don't have any documentation on the 1980-81 cars except that the build sheets continued referring to gold wheels color as 55, but obviously that build sheet is not used for opening cans of paint for the wheel.