What color is the factory amp wire?
One thing to note, most head unit wiring harnesses also have a solid blue wire. This wire is typically for power antenna or factory amplifier turn on, do not get this wire confused with the remote turn on wire with the blue/white stripe.
What color is the ignition wire for stereo?
and run positions and voltage should come back. This is the correct wire for Ignition/Accessory (red wire).
What color is the constant 12V wire?
Constant (yellow), also called BAT or Battery, provides permanent +12V power from battery. This allows the radio to retain settings (for example stored radio stations) when the ignition is switched off.