The arm rest bases in my '65 Coronet 500 were chrome plated but painted grey. Not sure when they got painted but it must have been a long time ago. I pulled bases from a '65 Coronet 440 and they appear to be chrome although most of the chrome is long gone.

I think I also figured out the red color. The pads from a 440 are a darker red than the pads from a 500. So it looks like Dodge used a different red color for the premium car. I confirmed the two red colors with a restoration guy who gave me samples of the two materials. He didn't know it was 440 vs. 500, he just knew that some customers need the brighter red and others need the darker red.