The arm discoloration happens on all the helm chairs from that era. They do sell a replacement cover that just snaps on. They look great but they are made of rubber and they tend to grab tee shirts and clothing when you a squeezing by in the cockpit. They are not cheap either I think I paid over a 150 for a pair. The dealers used to stock them but I heard recently they are not a Grady stock item any longer. I did see some on Ebay and the price was still high at 165. Somebody made a recommendation of using white ankle socks to cover them. Sounds like an economical solution and simple solution. If they get dirty toss them or wash them.