In PowerPoint 2010, you can format the background, change slides colors and tweak with many other formatting-specific options in Format Background dialog. In this post we are focusing on changing colors of all slides at once.
To quickly change the color of the slide, right-click the slide and select Format Background.
It will bring up Format Background dialog, from left sidebar, select Fill and from main window, under Fill Color, choose a desired color. Click Apply to All.
Now the specified color is applied over all the slides