Interesting. Is there a source for that? Never heard before about this age-related effect.
Lens transmission of blue (say <450 or <500 nm) declines with age - looks vaguely like 2% per year ages 20 to 60.[1] Thus reduced blue-yellow contrast perception in elderly. I don't know of any age-related change in red perception... perhaps those colors were off?
[1] "Fundamental Chromaticity Diagram with Physiological Axes - Part 1" (I'm unclear on CIE copyright, so no link, sorry), section 5.6.
Let me try to find some sources, this is so widely known and accepted in the photography (specifically astrophotography I guess) community that I have never bothered to look for sources.
It matches my (and a bunch of others’) experience though, for what it’s worth.
Sadly this is based on age. Younger people can usually see the red and purple colors in the Milky Way. Once you are close to thirty, this ability seems to go away.