How does firefox know when to display a green bar?

Recently I've been working on creating a self signed CA and had some success. Now I have a working CA with valid CRL server. The root CA has been deployed to all of my devices and had no problem.

But I have a question, I would like to sign SSL certs to display the green bar like other commercial EV SSL products. I looked into the parameters of those EV SSL certs but could not find any relevant variables. So I assume that the browsers have a separate way of knowing when to display the green bar.

I would like to know what it is and how to change it, especially for Firefox.