Change the background of TeXShop

Sometimes I need use LaTeX to generate equations in white color for my Keynote presentation (copy/paste from TeXShop). It is then necessary to change the background of TeXShop, otherwise nothing can be seen. There is a hidden preference just for this:

# defaults write TeXShop Pdfbackground_R 0.5
# defaults write TeXShop Pdfbackground_G 0.5
# defaults write TeXShop Pdfbackground_B 0.5

Change the values back to 1 to get white background or you can change it to any value you prefer.