Periodically someone starts to breed the blue egg gene into silkies. So its possible that one of your birds has that somewhere in its background. Or it could be stain from the muck you washed off (although for me muck-stained eggs are usually a patchy brownish colour).
The side of the egg I photographed only had a few dirt spots. The bottom half was the side embedded in the muck. So it truly had a greenish hue to the shell. I did put it in the incubator, so we'll see if I wiped it out in the water in about five days or so.
It was the first egg this color from the pen, so we'll see who continues to lay this color and I'll have to then go back to see where I got the egg that hatched the pullet. There are actually three different breeder's birds in that pen.
Thanks for the opinion.
Deb