Change the Halo Component (not the default) in a light in C#???

I've seen ways to change the halo on a light. But I want to know how to change the halo that is added from the "Add Component" menu. I've tried everything with getcomponent and using public Component! If I try something like this:

 lightHalo.Size -= 1;
 //lightHalo being the variable component that is my Halo component that I added

nothing works! What can I do? Keep in mind this command I'm trying to do is on the light object as a script component. Please help!