When your girl or a girl is on her period.
Mike: how you and your girl doing?
Danny: we doing alright but she got a code red right now.
Mike: oh damn do you need a place to hide? you can crash here.
Code red is often used by girls to secretly tell their friend that they recently got their period.
Girl: "code red, got it last night. I hate my life"
Friend: "omg that sucks"
When someone moons you (exposed their ass) and separates their cheeks to show you their sphincter.
Not only did they moon me, they separated their cheeks resulting in a code red.
A guy code that is used to secretly let other men in the general area know that a girl is on her period.
Guy 1: Emergency code red river commenced.
Guy 2: looks like we're going camping this weekend.
An idiot pilot that can’t fly a plane for the life of them.
Jesus Christ that’s a colour code red.
Did you see that tail strike? That’s a colour code red.