If hair greying was mostly caused by UV damage, I would expect that the pattern of greying would be even, and begin on the top of the head.
In contrast (based on my own unscientific observations!) greying typically begins in small areas, and often on the temples - not what I'd expect if caused by UV damage.
When most people think of age-related hair greying (which you referenced in your original post), they think of the phenomenon whereby hair follicles stop producing pigments that colour hair.
This is distinct from UV bleaching of the pigments in the hair.
> Sun radiation affects hair properties as color, luster, mechanical resistance, the content of proteins and others.
TLDR Yes it impacts color. Further reading can be found in the 75 studies that can be found in the references section.