In reply to William Hudson.

Chromlight is a more recent Rolex invention, first appearing in 2008 on the Deepsea Sea-Dweller. Between the introduction of Chromalight and the discontinuation of Tritium, Rolex also used green-glowing LumiNova/Super-LumiNova, which like Chromalight is photoreactive rather than radioactive. With that in mind, these changes did not occur across all lines simultaneously and they often coincided with the introduction of a new model or reference within a respective collection. However, certain watches like the black dial Milgauss feature both green-glowing and blue-glowing lume on their dials, so there is definitely some overlap in production between the different types of Rolex luminous material.