Stupid question

It doesn't matter, so long as you connect positive on the amp to positive on the speaker and negative on the amp to negative on the speaker. Kind of like jumping a car battery, but less dangerous if you mess it up.

If you do mess them up, it can sound bad. I have no idea why. Since the signal is AC, it's negative voltage some of the time and positive voltage some of the time, so it shouldn't make any difference. But I have heard them connected wrong and for some reason it does sound terrible.

Out of phase speakers do matter...it's all about "suck in or suck out" and if out of phase they "suck in" and that sucks.

Since the signal contains positive and negative values, the speaker is SUPPPOSED to suck in some of the time and push out the other part anyway. Speakers don't just move from neutral/zero to some positive distance from the voice coil. They also move backwards just as much. That's my understanding anyway, based on the fact that the signal doesn't favor plus or minus (otherwise it would be a combination of DC and AC).
Picture a bass note of 40 Hz with no overtones. A pure, repeating cosine wave. While it's above 0 volts, it's pushing the speaker. While it's below it's pulling. If you were to switch polarity, all you'd be doing is inverting the waveform. So it's still pushing and pulling. The only difference is you start off in the opposite direction. So for 1/80th of a second at the beginning it would be different. And somehow this makes an audible difference!
There must be more to it...

Hook up an electric bass cab backwards and see exactly what I mean. I worked with a bass player who did exactly that and the cab sounded pretty crappy until we re-wired it back to the proper polarity..."el sucko wrongo a mundo"...lower output, weird sound, and all of his fellow musicians pointing at him and laughing (not really as he was/is a very good bass player).

What Achilles said, and to add to that: The thing you don't want to do is hook one speaker one way and the other speaker the other way. Then when one is pushing the other is pulling, hence "Out of phase."
Hooking both "black to black / red to red", is 100% the same as hooking both "black to red / black to red"

Inverted phase?
Sucking out?

I believe you guys are making that stuff up.