Change the background colour of pages

Hi

I want to change the background colour of all pages from white to grey. I am not sure where within the style.css I should do this?

I thought it was here but it didn’t change anything

*,
*:before,
*:after {
/* apply a natural box layout model to all elements; see https://www.paulirish.com/2012/box-sizing-border-box-ftw/ */
-webkit-box-sizing: border-box;
/* Not needed for modern webkit but still used by Blackberry Browser 7.0; see https://caniuse.com/#search=box-sizing */
-moz-box-sizing: border-box;
/* Still needed for Firefox 28; see https://caniuse.com/#search=box-sizing */
box-sizing: border-box;
}

body {
background: #fffff;
}