Help! Liver turned green?!

I got some decent liver and cooked it tonight for the dogs (off the strictly 'raw' because of Zeke being poorly) I left some in the frying pan (covered) for the morning for the dogs and was planning to put it in the fridge overnight.

HOWEVER! It's turned green, is that normal?!

This is the first time I have cooked liver for them, I don't eat it myself...

YAK! I binned it, it can't have been safe, surely?

I cook liver for my dogs weekly and it can have tinges of green in it straight from the butchers, my dogs have never had any ill effects from it.

I think the green tinge in cooked liver is due to the bile salts. As long as it was kept in the fridg overnight it should have been OK.

Id have eaten it i assumed it was something to do with the iron content

I think thats normal, Its happens when Ive cooked my boy liver. Whats left over, I put in the fridge for him the next day and it has a greeny tinge to it.
I hate cooking it for him, but he loves it so much I do it for a treat for him.

YUP!! normal
I'd have eaten as I thik I might be the only one who loves liver!!

Oh b*gger! Thank you for all your replies! I'll know next time...what a waste!