Re: Popcorn ceiling - repair water stain
If the ceiling is unpainted, you can spray a bleach solution on the stain which will reduce or remove it. If the ceiling is painted, then you'll have to stain block the stain with a lacquer or pigmented shellac then repaint. Color matching the texture will be difficult if not impossible if you don't have more of the original paint used. You might be able to get it close, but not likely perfect. Also, if the ceiling paint is more than a year old it's going to be well coated with dirt and dust so that any new paint you add will stand out. It is likely that you'll have to paint the whole ceiling.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!