change css background with jquery?

change css background with jquery?

hey there! i am trying to learn jquery/javascript in general and need a little help. i want the background image of my site to change each time the page loads. i have 4 images (same image in 4 different colors) that i want to rotate between. with each image, i want a cooresponding background color.

this is in my css now:

html {
background: blue url(../images/bg_blue.png) no-repeat;
background-position: center center;
}

and i want to 3 other options for the background property, for example:
background-color: red with background-image: bg_red.png etc.

does this make sense? i've tried a couple of things...but im just not quite getting it. if anyone can help me i'd really appreciate it!

thanks!

shaina :)