I quick-picked some green beans and a week later, the garlic in the jar had turned blue green, turquoise, smurf color. I googled it and brought up a reddit thread that said it's safe to eat.
I did not eat it.
This is true! I'm no chemist but I make paint pigments from plants rich in anthocyanins, which give them colour. Popular mordants (things that helps a colour stick to fibre) are copper salts, which can brighten the colour or make it more blue/green.
And, an old kind of pigment, verdigris, was made by hanging pieces of copper in closed containers with vinegar, where the vapour would cause a blue/green/gray salt to form.