I had a hen that laid a "mauve-colored" egg. She was a Welsummer. The egg itself was actually brown, but the blume on her egg that gave it a "plum-colored" appearance. I could never capture the color on camera. She was a hatchery chicken. I got lucky I guess.
I have a wellie/OE that does the same thing, hers is brown but has a pink (I don't know the word for it, hue maybe) color. Hers is also dull in appearance not shiny like the others. Muted pinkish brown? It adds variety to the basket so I like it!