1969 engine color

I was just sitting in my E-Z chair by the fire, and I got this question that popped into my head.
Does anybody have an answer on where & when the auto makers decided to paint the engines in their brand of automobile? How did they decide upon the color? Some one had to decide to do this, if it had been left to the bean counters, you know they would have nixed the idea. (saving money) Was it a monkey see, monkey do? Who was the first to do it? Inquiring minds want to know! Does anybody have any ideas or theories? I'm sorry for hijacking this thread, but when the thought came to me, this was the thread was on top of the list.