How to change the colour of the background

 Hi
When I resize a pic and make it smaller I see a transperent background, which will get black when I apply. Where can I change this into white or grey?
I tried it with this css file: cropper.min.css but that doesn't seem to be the right file...

P.S. I would be nice if I could "search" through your help desk. Perhaps this question was still there..

Hi Lefteris,
no problem.
concerning my problem. Is there no way to fix that? The best way would by that I can entere the colorcode I want. So that the this part of the pic can get the color of my page backround. In the most cases white will be more used than black i suppose. With black bars it looks like an old cinemaskope film on TV. ;-)