Beach Mats

Hello All: Wondering if anyone can help me? I recently purchased some beach mats from the dollar store. I plan on hanging them along the back of my canopy, (instead of looking at the wall of my house). I would like to paint some sort of design or flowers on them, but not sure if the paint would stay on with the rain. Has anyone out there done anything like this? If so what paint did you use? and do you need to use anything to seal it? Any advise would be
most helpful. Thank you