How do I use custom fields to allow frontend Admins change banner color and logo

I am using the plugin Frontend Pro and I would like to use custom fields to set up a form for admins on each multisite so that they can go in and change theme options for their site without having to use the Wordpress dashboard. The ultimate goal of my entire project is to move everything to a frontend editor for admins so that we use Wordpress without looking like we do... Not an uncommon request from clients, but this project is bigger than any others I've done. So even a general lesson on how to 1) figure out how the theme options are saving the data (if it's already a custom field or not), 2) how to put that function into a custom field so I can use it with Frontend Pro, 3) etc...

I'm sure there are all kinds of things I'll need to ask, but for now: how do I use custom fields to allow frontend Admins change the banner color and logo?

I'm using Sportsmag Pro from Magazine3

Thanks everyone