Sorry to hear you didn't get any of the good stuff. It was amazing weed and I have not found a replacement. There has to be a way to get that cure they didUnless the plant is purple, to begin with it will not turn purple when dried. The Colombian Gold I got in '79 was picked early. Immature seeds. Not great stuff. Poor farmers doing what they could to survive. Not great growers carefully tending the plant. 90% of pot will turn yellow or brownish yellow if you leave it in the sun or just in a jar long enough. I have seen both so I know.
Cutting the stalk, girdling, or lack of fertilizer is not great farming practice. Easy and common. Most stuff from 70's was poorly grown and handled after.
I am growing real Colombian Gold now. The fan leaves turn yellow with no lack of nutrients or girdling. Buds in the jar get yellower,brownish by the day.