Interesting article with some key illustrations on Blaschko’s Lines, a pattern of invisible stripes which mark all human skin. These are naturally occurring growth rings which appear on every human body, and can be made visible to us under ultraviolet light.
Looking at the images suggests to me that an alien with an eye configured to see in a slightly different color spectrum would easily see these lines, and see all humans as marked with variegated patterns, like tigers or zebras.
Perhaps they’d think we were pretty.
Or that our skin made lovely fashion accessories…