Standard rose gold (also called pink gold) is 18-karat gold (75% pure gold) alloyed with copper (and a small amount of silver). The copper provides the pink colour. The chemistry has a problem: copper oxidises slowly under exposure to chlorine, saltwater, sweat, UV light, and skin oils; over 5-15 years of wear the copper-rich surface oxidises and the watch case takes on a yellower or more orange tone, losing the original pink hue.
Rolex's response was Everose, introduced in 2005 (initially on the Day-Date 36 ref. 118235). The composition replaces a small portion of the silver-and-copper alloy with platinum; the platinum content (proprietary recipe, not publicly disclosed) acts as a colour stabiliser, slowing the copper oxidation rate dramatically. Modern Everose Rolex watches retain their pink colour after 10+ years of daily wear in the way standard rose gold does not. The trademark name 'Everose' is Rolex-controlled; competing pink-gold alloys at other brands are typically generic 18kt rose gold with no special stabiliser.
