Radio help

Let me start off by saying I appreciate all the help here, it's invaluable to a guy like me. I've been asking interior questions because I plan on replacing the instrument cluster, center console, radio and heater controls, dash pad, wiper linkage and defrost vents in my 73 Dart Swinger. I figure it would be stupid not to try and do it all at one time when its completely apart. So now a few radio questions for you guys who have been there before.
I bought a refurbished chrysler am/fm radio from Wards Classic Car Radio, nice guy, decent price. The previous owner cut a freakng hole in the center console and installed a crappy stereo. I have never installed a car radio myself, so.....what are the red and orange wires going into the plastic plug? And what are the green and black wires for? Also on the side of the radio, is the nut there for securing the radio? And what it the small round hole? Thanks in advance for helping me on my journey!

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