Phatch hit it. The pan could have trace amounts of aluminum or other reactive metal. You have acid and sulphers at work here. If stainless steel, eggs will turn green. The ph factor in sulphur in egg does this, mixing in a bit of sour cream will stop it ( ADDING A FORM OF ACID TO COUNTERACT REACTION)
It is a nonstick shallow roasting pan. I know it has something to do with the lemon juice and garlic because this has happened before in roasting trays of all kind. It seems to be the garlic that is turning green.