Patio concrete black spots

I don’t have experience with that particular product. However, I had mine stamped to look like stone a couple of years back and like the heck out of it. They first put about a quarter inch of new concrete. While it was wet they stamped it to give the texture of stone and also put some pigment down to color it.

I say all of this to tell you that you may be able to comoflauge any future growth of that shite.