Change Link Colors From JavaScript?

I'm writing a FireFox extension and I have the dom and therefor the
links[] collection

window.getBrowser().contentDocument.links[i]

Is there a way to change the color of these links based on the stuff I'm
checking for from the JavaScript?

For example. If I have this loop
var number_of_links = window.getBrowser().contentDocument.links.length;

for (var i=0; i < number_of_links; i++)
{
var domain = window.getBrowser().contentDocument.links[i].hostname;
//Check hostname here and change color
}

how could I change the links color?