Can Hesalite crystal get darker over time?

More specifically, can the Hesalite crystal on an Omega Speedmaster form a dark tint from UV exposure, etc., that makes everything underneath it look darker? For example, I recently bought an Omega Speedmaster where the hour marker tritium lume looks dark/almost brownish color. However, when seen in the sunlight, it shows it's pumpkin glow.

Then when I compare this Speedmaster to another Speedmaster with Hesalite as well, the hands, lettering, etc. all looked like it was underneath a dark tint when compared to other Speedmaster. I don't know if my eyes are tricking me since dark lume makes the hands and lettering look dark as well, but just wondering if I should replace the Hesalite. The Hesalite looks otherwise very clean with minimal scratches.

Old hesalite crystals can definitely yellow with time, I've owned a great many of them that had a very yellow or brownish tinge to them and were clear after replacement. I'm not sure how new ones perform but I've never seen one on a modern Speedy go yellow myself.

How old is the watch we're talking about?

It's a 105.003 with at least a 15 year old hesalite crystal compared to a 105.002 with a brand new hesalite. Sorry I didn't include pictures because it doesn't take very well to compare.

I just don't know how this watch can look so different head on and from the side in different lighting. Maybe I'll just replace the hesalite just in case.

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I guess the other question is was the hesalite fitted a brand new one from Omega, or was it NOS vintage stock?

The 105.002 had a hesalite crystal that was NOS vintage with a silver retention ring, but it still "looked" more clear than the 105.003 that I posted above.

quite simple: Its a "dark side of the moon" 😉

Nothing to do with the crystal imo. It’s just slightly dark/dirty lume that looks different under different lighting conditions