You have your work cut out for you.
The standard
JSF droplist control generates a standard HTML droplist control, and the HTML droplist doesn't allow styling of individual items in the list.
In order to get that effect, you'll need to provide javascript code that looks and behaves like an HTML dropdown list, but adds per-item style options.
There might be something out there in one of the specialized libraries for that, but I don't know of any myself.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.