Remove colored box around table on page

Hi there, I was wondering if there is an option to remove the colored box sitting around Tables. The main background color of the page it white, but the Table is displayed on the page with a Grey-ish box around it. I would like to have the entire page-background to be white. Any fixes to this problem? http://duimelijntje.nl/leren-schilderen/schilder-cursus/ Thanks in advance.