Once you go black, you won't go back to red.
I've used the black tip several times and feel that it's very effective in removing the top layer of skin when using the PMD.  I don't know how you could use it & not feel anything, it's pretty coarse.  I wouldn't use the black tip every week, but it's great for 1-2x per month.  The yellow is more suitable for non-face sanding (like cuticles, elbows, feet, etc).
Rating: 5 stars