Are people of mixed black and white ancestry who along with mestizos make up more than two thirds of panama's population.

I believe the answer is: Mulattos

In the past, Panama was colonized by the european empire due to their natural resources. In the process, The European empire bought a lot of slaves from Brazil and Africa to work in the plantations.
As the years goes by, these three cultures assimilate with one another and make up the majority of population in Panama.