On that part red and green are the phone line, black and yellow are aux power.
What do you have for an MPGuion?
If you have one of the kit built units the phone module would have relevance and this link is the information your looking for.
http://spiffie.org/kits/mpguino/installation.shtml
If you have one of the newer pre assembled units or a scratch built one there is not a modular jack built in so the wiring would be whatevery you set it up to be.
Mike