IMO, there isn't anyone I know of, that from photographs alone can ascertain how much or how little mpc pressure is being used, and that includes Physicians and Surgeons. As for "red ring" after playing, on some it will be noticeably visible for a varying length of time from person to person, but no player I know can truthfully tell me the physiological cause is always pressure. For some it is silver allergy and for others it is just tissue sensitivity ... and I'm of this latter category whereas I am diabetic, but I'm an advocate of using as little pressure as possible and not for this reason. Seemingly, my endurance is improved with less pressure viz just enough to play the note correctly and comfortably. I was amused, but not laughing, when I heard one male player tell me he cushioned his mpc with his mustache to avoid "red ring". Especially, when I played my euphonium or a tuba and had just a day's growth of beard, a stubble, the skin between my lips and nose became quite irritating and reddish beyond the area of mpc placement but dissipated when I ceased playing within the next half hour as helped along with the application of aloe gel. After playing now, I apply the same also to my lips. In summary, some show mpc impression and some don't. If such mark is lasting, or bothers you, I too recommend consulting with a physician as others have suggested.