Learn to blend in. I personally don’t like to swim or sauna with people who are fully clothed, including wigs, head gear and shoes.
I didn’t see where the notice said people with dark skin were not allowed.
Dress for the occasion. Black people know how to do that – they do it all the time.
No wigs, robes or sandals in the pool. They shouldn’t need the rules explained.
Somebody’s looking for some free money, not an enjoyable pool experience.