Radio Connection?

My 72 has a new wiring harness that has the original style radio connection with black yellow and grey wires. My wife bought me a new replacement stereo from Ecklers and it has individual wires. It has battery, Ignition and ground. I know black is ground but what about yellow and grey. Is one ignition and the other one battery? The yellow is hot when I turn the key on. All the other grey wires are for lights in the dash. I need help!!!!

I found an old post that said yellow is power and grey is illumination. Why does the new one have a battery and an ignition? Now I'm more confused.

Ignition is to turn it on and off with the key in ignition or accessory position.

Tied the battery to my clock and taped off the grey wire so no problem when lights are on. Got it working now.