on a page how do you get three color strips as a background yellow grreen and blue

body {
width: 100%;
min-width: 1100px; /*containment*/
margin:0 auto; /**centers page**/
padding:0;
background: #FF3;
color: #000;
font: 1em/1.5 "Lucida Sans", "Lucida Sans Unicode";
}

this gets me a yellow background but how do i modify it to add a green and blue stripe accross the background