The Panopticon/Colour scheme of pop-ups

The colour scheme of those pop-ups that appear on the bottom of the page is problematic. If the pop-up is the right size, then the x to close it ends up being white and white and can't be seen. If you click in vaguely the right area then it will close, but there's no visual cue. The first pop-up I had I didn't end up closing for a couple days because there was no visual evidence as to how and I didn't click around trying to find out because I didn't want to go to wherever the link sent me. Now that I think about that, I was being kinda silly-I could always navigate back. Anyway, this isn't an issue with a lot of the pop-ups because the shape of them means that there is some differentiation, but there is at least one shape that is problematic.