Distributor cap color question - what year

What year did Mopar go from the black distributor caps to tan? A friend picked up a 66 Chrysler Newport survivor and is cleaning up the engine compartment. It has a blue distributor cap. I told him to put a black cap on it but then questioned my suggestion. I am 100% sure my uncle's 66 Dodge Coronet had a black cap the day he picked it up but I also remember (but my memory is not as certain on tnis car) my other uncle's 66 Chrysler 300 having a tan cap the day he got it. Anybody got any statistics on change dates?
Thanks!