1991 S10 Blazer 4x4 Alloy wheels

I noticed a 1992 S10 Blazer 4x4 with factory 5-spoke 15x7 alloy wheels had black accents on the spokes and inside  the lug nut holes.  My 1991 S10 Blazer 4x4 alloy wheels does not have those accents. The origibnal 1991 4x4 wheels are as cast, machined and clear coated. Am I correct to assume all the alloy wheels received the  black accent treatment starting in 1992  or  was it a specific make such as a Bravada, Chevy  or GMC that received the black accents?

I have several spare alloy wheels that I want to get restored and the restoration company asked me if I wanted the black accent treatments applied to them before they are clear coated.  I like the black accents but I do not want to apply them to any of my  1991 alloy wheels if it is incorrect for that year.