The 5131R is probably the warmest of all enamel worldtimers - not a big news here but RG goes well with the warmest colors of the enamel. Definitely better than yellow gold. I am not a worldtimer lover but I would have a hard time deciding between WG and RG. The blue enamel parts go well with WG but RG offers a great contrast against the grey and the blue of the hour disc and matches well the warm parts of the enamel, in addition it could be more legible.