Raid Leaders - What do this mean?!

Hello,

I've been searching everywhere and can't seem to find the answer to this.

When you search for a raid and up comes the list of raids available, when you hover your mouse over the raid a box pops up to the left with the Raid leader's stats etc. I was just wondering what the green/red/yellow boxes under his name mean? I get that that correspond to the raids however does green mean that it is available now or does it mean that he has completed it already?

Sorry if it's already been asked here.