I have just had exactly the same thing! Almost luminous green! Have just googled and saw your post as I’ve never seen anything like this. Hubby thought I was trying to poison him but threw it away. No strange smell to it, a couple of days old, mud wiped off and unrefridgerated. White shelled egg. Haven’t a clue why but unusually not sold many duck eggs lately. I’ve just cracked every single egg I have and all are perfect. Weird, very weird!