Hi
Hair display is very bad in particle edit
Yes, I don’t actually know why we always display hair particles black when in Particle Edit mode. It seems like we should be able to just use the same display as we do in Object Mode.
My guess is that this is simply a remnant from 2.79.
Did you try selecting them (shortcut = A)
Particle edit for grooming its not the best looking thing, but shouldn’t show a black block.
By the way if that grooming in the first image of the post are all guides, those are a lot of guide for that shape.