Just a thought about the cause of aged luminous on vintage rolex/tudor

[harry in montreal]

Could yellowing and color changing luminous be caused by the oil that was used in the movements? maybe the oils that were used by rolex from the factory was more translucent, and smaller watchmakers used yellowish oils. i just had this thought. many of us hypothesize that the color change is caused by water infiltration... maybe this is not entirely the case.