realistic model 12-1930a

Does the radio have a fader control? If the answer is yes then the radio is a common ground circuit as was common back in the day (grrr.... shows how old I am). A common ground means the - speaker wire on each speaker is actually grounded to the chassis of the vehilce. In most cases they were attached to the ground wire behind the radio. The red and red / white are more than likely power and ignition, black is more than likely ground and the orange may be an illumination or remote on wire / power antenna (unlikely for the latter) unless it is a digital radio. I have not seen a old radio like this in years and I cannot find my notes that date back that far, but this should point you in the right direction.Top Secret, I can tell you but then my wife will kill me.