change background color in javascript

The only good style of defining colors is CSS. Therefore, the only good way to do this in JavaScript is changing or adding the style of the element. And one of the most convenient way of doing this is using jQuery:
http://en.wikipedia.org/wiki/JQuery[^],
http://jquery.com/[^].

You can use the jQuery .addClass, .removeClass or .toggleClass methods:

myElement = $("#myElement"); //find element where the element is marked with id="myElement" in HTML
className = "yellowBackground";

myElement.addClass(className); //make red
myElement.removeClass(className); //restore previous classes and hence CSS properies

//or

myElement.toggleClass(className); //toggle it

Naturally, you would need the correspondent classes in CSS:

.yellowBackground { background-color: yellow; }

Please see:
http://api.jquery.com/addClass/[^],
http://api.jquery.com/removeClass[^],
http://api.jquery.com/toggleClass/[^].

Learning jQuery is easy and a kind of fun. Start here:
http://docs.jquery.com/Tutorials[^],
http://docs.jquery.com/Tutorials:How_jQuery_Works[^].

—SA