Examples: “Is something wrong? You look a little green around the gills.” * “I’m feeling green around the gills. I’d better step outside and get some fresh air.”
When you say that someone is green around the gills, what you mean is that he/she looks out of sorts. In other words, the person looks sick or unwell. The person feels like throwing up.
It’s possible to say `blue around the gills’ as well. It means the same thing.
Example: “Ever since eating the chocolate cake, I’ve been feeling a little blue around the gills.” * “I’ve been feeling blue around the gills since this morning.”