Microdermabrasion, whether with a diamond or crystal system, removes the superficial layer of dead skin called the stratum corneum. This is usually accomplished in one to three passes. Redness, like a supeficial sunburn, after microdermabrasion is not uncommon and should subside over the next 1-2 days. In fact, this slight redness is a marker that the treatment removed most of the dead cell layers and you will likely see an improved benefit because of it.
Your previous treatments were likely too superficial to cause any redness. Underlying damage to the deeper layers of skin is very uncommon with microdermabrasion and would usually have weeping, blistering, crusting, bleeding, or significant pain like a deeper burn.