As a side effect of a meditation technique I use, I several times daily look for one each of objects in my environment that are red, orange, yellow, green, blue and violet. Blue takes a long time to find and purple takes longer. If sci-fi screens are blue bc of rarity, wouldn't purple be a choice, too?
I think blue and purple are strange and rare. But purple probably has too many connotations with little kids' arts and crafts or quirky old people.
And we don't have to limit ourselves to what is natural, we can consider things in the man-made environment. We tend to make many more things blue than we do purple.
Looking around my desk:
Blue things: static mat, phone LED, supply label, USB cable, sticky notes, Outlook, mouse pad, pen, bananajack, map, medicine bottle cap.
Purple things: coffee mill box, cover of notebook.