var backColor = new Array(); 
backColor[0] = '#ffffdd';
backColor[1] = '#99CC66';
backColor[2] = '#FFFF66';
backColor[3] = '#996600';
backColor[4] = '#E5ECF2';
backColor[5] = '#FFFFFF';

function changeBG(whichColor){
document.bgColor = backColor[whichColor];
}