Water Stain on Ceiling

I got mine dry and found some chalk that matched the color and was going to wait till some idea came into my head of really what to do. 4 years later and nothing upstairs in my head yet, but the chalk is still up there. One light shows a little shadow depending of the angle of how I look at it. This was the chalk that kids write on sidewalks with, took awhile to find right color. I've subscribed to this because I'm still waiting for the best recourse of action. In the past on different RV's I've tried wet/dry vac and bleach and etc. Chalk has held up the longest and I used it as a "make-do" until I found something better.