A 2017-12-30 NYRB article mentions "blue chickens sold in state grocery stores". An anecdote about life in the Soviet Union also mentions that "[b]lue chickens would sometimes be sold outside" the "regular small 'grocery stores.'"
Why would chickens be blue? Was it due to some sort of chemical treatment?
For the benefit of those who think that by "blue" chickens they're referring to chickens with a few feathers that might at a stretch be considered blue, here is the fuller quote from the NYRB article:
Nor would the private markets sell mayonnaise. They’d sell everything else—poultry birds proudly displaying curly yellow fat in their cavities, as if in reproach to the bony and blue chickens sold in state grocery stores.
I imagine that these chickens were plucked in order for one to tell that they had "curly yellow fat" or were "bony".