Traveling from the US to Cuba
If you travel to Cuba from the US you need to have the pink visa. Once you travel from the US to Cuba, all the US rules concerning traveling to Cuba apply to you. It is still not allowed to travel to Cuba as a tourist. This means you need to travel under one of the 11 accepted reasons. If you go back to the US after your trip to Cuba, it is possible US immigration will ask you question about your trip, to see if you held up to the accepted reason for traveling.
Traveling to Cuba with US nationality
If you have the American nationality, you must have a pink visa at all times. From October 2022, it will be mandatory for Americans to show the pink visa upon entry. It does not matter from which country you depart. For example, if you travel from the Netherlands to Cuba with American nationality, this will have to be done with the pink visa.
For non-US nationals, the pink visa is only required if you are traveling directly from the US to Cuba.