One common manifestation of color perception differences among
people is seen in the undergraduate laboratory experiment in which
the Balmer lines are detected. These tail off into the ultraviolet,
getting progressively denser. I don't know how many Balmer lines I
can see now (we don't do the experiment here) but the variation is
large, from three lines for an old codger to five for a youngster.
As I recall from my undergrad days we had to generate the hydrogen
used in the discharge and flow it continuously through the tube.
That may be the reason it isn't done in undergrad labs here at SFU.
The lens of the eye yellows with age, becoming less transparent in
the violet. Physicists have reported "miraculous" improvement when
their lenses have been replaced for correction of cataracts. They
see more Balmer lines.