Egg shell changing colors

[SillyRooster]

One of our Barred Plymouth Rocks laid an olive colored egg. Same color as our young easter eggers. This is the second time. Not sure if it's the same hen. Our neighbors have Rhode Island Reds that laid eggs olive colored eggs during the coldest days of winter. What causes this, should we be concerned?

 

[Ol Grey Mare]

As you say you are not sure it is the same bird, how are you sure it is a BR producing the eggs? Crack one and post a photo of the internal shell and also post a photo of the birds in question. External shell coloration can vary throughout a hen's laying cycle, but the internal shell color will not vary as brown layers lay a white egg coated with brown pigment and green layers are producing a blue shell (internally) that is coated in brown....which is why seeing the internal shell color is going to be key in determining if you are correct in your assumption regarding the source hen of the eggs you have received.

 

[SillyRooster]

This is the inside of the egg. This flock is three Barred Plymouth Rocks and three Ameracaunas. The roo is a handsom Rhode Island Red.