I heard that they work really well. But I'm not sure how it works. Are there different shades of green for different color skin? How would you apply it?

its called 'green' concealer means its not harming the environment...

Innoxa have a concealer with green. I think it's meant to counteract the dark pigment in the skin or something

green is to help u cover redness and it works well sparingly and with a neutral concealor or powder...(preferably mineral) over it to get the look you want