Interesting.
I was a technical services manager for Stihl Canada in 1989, even had meetings with Hans Peter Stihl.
I never heard of the legend of the "extra performance " flagged with a red colored master control switch. 
LOL. It's probably more a case of them using red switches during the time frame that the 'best' (meaning less EPA detuned) versions of these saws were being built. The change to black plastic switches may have come around the same time as the other changes....