what would happen if the sun's magnetic field and the Earth's magnetic field reversed polarity together?

Well, that in all likelihood is not possible. Reversals of Earth's magnetic field seem to take at least hundreds to thousands of years to complete. It's difficult to determine whether this is happening at any specific time, because the magnetic poles wander about constantly, and Earth's magnetic field changes in strength constantly. There's been at least one study suggesting that our planet might have undergone a "rapid" geomagnetic reversal at some point in the past, but even that supposedly took several years, and the evidence provided for this claim has yet to be studied in depth or accepted by most geologists, AFAIK.

If a reversal of Earth's magnetic field somehow, against all odds, coincided with an 11-year reversal of the Sun's polarity, I expect we might see an increased exposure to solar radiation for a couple of years, resulting in far more frequent interruptions in communications and electrical systems. Other than that, I doubt the effects would be directly harmful in any significant, long-term sense. Maybe carry some sunscreen when you're outdoors for long periods, but everybody should do that anyway.

The effects wouldn't be any different than any of the preveious pole reversals of the Earth, since it takes thousands of years to complete, several solar polarity 'flips' have occurred during each Earthly one.

Nothing would happen.

black people would be white, and whites black