If I saw five men in black masks walk toward me, I would react according to my surroundings. At a hospital, I would wonder why the medical team changed from white to black. In an isolated area, I would get out of their path and probably run to safety if I felt threatened. In an airport, I would think that they were overly sensitive about germs or were diseased and required to wear masks.
The last time I saw a person in a mask was on the outside of a hospital. I did not react much, except a brief stare, and walked on my way. Before that, I saw a cook wearing a mask. I discovered that she had a cough and wanted to avoid contaminating the food she was preparing. Before that, I saw mowers and assumed that they were sensitive to allergies. Black masks would not make much difference in some surroundings. Why would you get scared?