About a week ago we ran out of nesting materials for our chickens. We had just cleaned out a bunch of files so had a lot of shredable paper and thought we would give that a shot in the boxes. It's worked ok, though it's not ideal, and we'd planned to at least finish the papers we have before getting more bedding. But this morning when I went to make breakfast I was shocked (and quite discussed I'll admit) to find the yolks were a greenish-gray to black color. We cracked half a dozen just to see if it was one bird or another, but it didn't matter, they were all discolored. I broke the yolk to see if it was the same all the way through and was relieved that it still had it's nice golden color on the inside. We'll be getting straw for the boxes as soon as we can. I'm reluctant to eat them but the only thing that seems wrong is the color. They smell fine and the only thing that has changed in the last week is the paper. I'm curious if anyone else has experienced this. The birds are locked in the coop as winter in Minnesota is just to nasty for them outside. I've been raising chickens for about 7 years and have never seen anything like this. Thanks in advance.