No. It is simple. The radio box is ground. There is no separate ground wire. The red wire goes to switched 12V IE accessory. That powers the radio. The orange wire ties in with other orange wiring in the car, which is dash dimmer controlled dash illumination
The other two are speaker. You should check continuity to the radio case, one of them may or may not be grounded to the case and probably is. You must be careful with this if you are going to an "amp" but I don't know why you would do that with an old mono radio. If you DO use an amp you are going to have to find out if the input to your amplifier is grounded on one side. "It might not" sound all that good because an amplifier input is low level, and what you have there is fairly high output coming out of the car radio. That will be an experiment. Also, radios are not designed to be operated without a speaker "load." Sometimes this can damage audio output circuits
