It's been a while, but I tend to not pass TSA's security without at least a pat down at this point. I wear cloth, not disposable, and they tend to be a little damp from sweat by the time I hit security. If I was to do it now, it would be a little more than that....
You mentioned "red". When I've seen the screen it has been a yellow box over the area. Maybe that's the difference between a pat down allowed, vs going further.
My worst was years ago, leaving a warm vacation area, where I had an afternoon flight home. I had used sunscreen during the day.... Combine that with damp extra cloth layers, I had the private room visit. Eventually they cleared everything. I'm not sure what it took to clear their chemical analysis of the sunscreen.... Since that was more of a liquid, I had my spare sun screen in a sealed plastic bag in my checked in luggage and not in the hand carry.
In addition to normally getting hit with the pat down, I also carry a bottle of baby power in my hand carry luggage. I now always pull that out so it is separate at the x-ray so they don't have to dig through that to find the bottle, to perform the "required" additional chemical checks on it. Brand new bottles (such as at the start of a trip) are basically guaranteed to get pulled for further inspection.