I'll pinch Maikel to take a look at this and decide what would be best in terms of color and design. It would help if you could post a big 1:1 version of the window and mark which segments can be altered so that he may decide on the best combination. As for the text, I'll work on that in the meanwhile.
The size of the window should be as small as possible. It would be a little annoying if the window would cover half the screen. Off the top of my head I'd say somewhere between 350-400 pixels in width, and whatever will be required in height by the text.
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