The main problem is that you can filter and re-order the resultset on the fly, so you can't define the coloring using the onload method of the page, because that's only fired once.
But when you have a Link Column in your report you can use the onload event of the image in that link :
<img src="#IMAGE_PREFIX#edit.gif" alt="" onLoad="Alternate(this);">
And define in your Page HTML Header:
You can see the colorful result here: http://apex.oracle.com/pls/otn/f?p=ROEL:ALTERROW