Christian Effenberger has doubled up to release Mapper.js 1.0, a library that allows you to add automatic area highlighting to image maps
on webpages. It uses unobtrusive javascript to keep the code clean.

It works in all the major browsers - Mozilla Firefox 1.5+, Opera 9+,
Safari and IE6+. On older browsers, it can use “jsgraphics” from
Walter Zorn (if installed), else it’ll degrade and visitors won’t
notice a thing.

You are able to create an image map, and then define the colors through the simple CSS class microformat: