Wrote Nora Ephron, a while back.
I'm finding that this morning, because Dick Gephardt is in the news today, blogged here, where William asked "How did Gephardt spend so many years in public life without being
relentlessly mocked for his orange hair. I guess back then people were
more tolerant of orange hair...."
Also, Bob Shrum, in "No Excuses: Concessions of a Serial Campaigner," describes a Dukakis ad (in 1988) that mocked Gephardt by showing a "gymnast with comically dyed orange hair dressed in a suit... trampolining and tumbling forward and back and forward and back again" with the voice-over describing Gephardt's various flip-flops.
So orange hair got mocked, even in the old days. It's not just something invented recently to attack Trump. I certainly remember Reagan's hair getting mocked, especially since he denied dyeing it. The much-repeated joke attributed to Gerald Ford was: "Ronald Reagan doesn't dye his hair, he's just prematurely orange."