No Blue Eggs

[ChocolateMouse]

They cannot. Sometimes the shade may change a bit from lighter to darker, so you may be mistaking green eggs for blue or vice versa but an actually blue colored egg is very unlikely to shift dramatically enough to be considered green.
The surest way to tell if a chicken is laying is to isolate it for a couple days and see if it lays an egg.

 

[EggWalrus]

I have 2 young easter eggers. They laid pretty blue eggs for about 3 months and now the past 2 months I never get a blue egg. Can they change the color of eggs they lay? I have 2 olive eggers so there are usually 2 green eggs everyday & I have several Marans. Except for the 2 green eggs daily, the rest are brown eggs.

EEs and real Ameraucanas that I have had are prone to quit or slow down laying in winter. Not all will quit but some do.
I used to give them supplemental winter light to force them to keep laying, but I have quit that. It is better for your birds to get that winter break that allows them to rejuvenate their egg maker (girlie parts), plus it gives me a break from collecting, cleaning, packaging and selling all those eggs! They still give me enough for me to eat every morning.

 

[EggWalrus]

They cannot...
The surest way to tell if a chicken is laying is to isolate it for a couple days and see if it lays an egg.

It might take more than just a few days, with some girls. Chickens are Creatures of Habit, and when their routine gets interrupted, it can interrupt their laying.