My G260s both have a dark grey, almost black, ring. Both are from 2014. No idea what colour signifies.
View attachment 878730
My R195 has a light grey ring. Also from 2014.
Note the R195 ring has a tag on the outside that fits into the reg to stop it spinning when screwing the cover on. The G260 ring has tags on the inside of ring to clip into the cover and spins freely.
View attachment 878731
No need for a yellow cover. I actually recently changed my green “nitrox” R195 cover to a boring black one (still has the nitrox decal on the purge).