Rolex Deepsea Lume

Lume is an abbreviated term for the luminescent material used to distinguish the watch hands and hour markers from the dial in the dark. For the past few years, Rolex has used their Chromalight luminescence, a blue tinted luminescent material shown in the photo above on the Deepsea model. The reason they chose the color blue is that it is the last color distinguishable in the depths of the ocean. Previously, the watchmaker used a green tinted luminescent material called Super-Luminova. The GMT-Master II in the photo below shows the green lume that was used prior to Chromalight.

Rolex GMT-Master II Lume

Super-Luminova is the brand name for the strontium aluminate–based non-radioactive and nontoxic photoluminescent pigments invented in 1993 by Nemoto & Co., Ltd. of Japan. LumiNova pigments replaced radium-based luminescent paints in the watch industry and for other applications, like scientific instruments and signs. The pigments are activated by sun or artificial light to glow for hours at a time. According to speculation on the forums, it is believed that Rolex still uses paints from Nemoto in their Chromalight luminescence, even though it is branded as a proprietary material of the watchmaker. 

Rolex Yacht-Master II Lume