My own Link CSS Style for menu Item

Hi,
I want to add my own link css style for menu item, but I can't.

I add my css code to css override in template, and I also add class in menu item.
When I chack by firebug I see class like "haschild" or "first" but I do not see my class.

This is my css code

.cat-green {
color: #00cc00 !important;
}

How exactly did you add the class to menu?