Custom Google Search Popup Styling

I have benefited greatly from looking at the posts here, but I am unable to find what I am looking for.

I need some help with styling the popup results from CGS:

At the moment, the dialogue appears (with no results at the moment), and I would like to change the opacity of the box, the ugly yellow results, and so on. Not to mention the “close” not fitting in the window.

I’m not even really sure if I should call this a popup, a dialogue or a window. Hopefully you know what I mean.