The Mismatch:
I think the reason for the slightly different shades of Coppertone and other vintage appliance colors was that it was an attempt to keep a customer in the "family." If Sears didn't match Westinghouse exactly, then a persnickety customer was a little more likely to buy all their majors from one company or the other, instead of mixing and matching.
Only customers choosing White got to do that freely back in the day.