When viewing older GM cars and trucks we see both colors of park light lenses. There seems to be no consistency that gives us the proof of what is actually correct, however, it is easy as remembering a year.
Beginning in 1963, federal regulations required park lights to show an amber color. Today, companies reproducing original clear lenses find it easy to run more in the same die using an amber additive. Therefore, in GM trucks most 1954-62 clear lenses now can be found marketed with an equivalent amber style.
One exception is the 1969-1970 Chevrolet truck. Originally it came new with clear lens but behind them are amber park light bulbs giving the required color appearance when illuminated.