If you go into the window color box you were in to try to change it, click the dropdown menu and select "Active Title Bar". Then you should be able to change the color of the window. Here I took a picture of the box and where to select the option:
EDIT: I just tried this again, and this time it isn't working, however when I minimize or maximize it, the bar is green until it finishes the animation, then its light blue again.