Pebblz Large Sink Mat 5 "TAKE NOTE" Miss Savin 04 October 2016 I've read a number of customers complain that the mats stain..I have used these mats for years. They discolour over time which is natural however they DO NOT stain. You need to remove them whenever you use tomato based sauces or anything that you think will stain plastic. The mats are porous of course they will stain. Even my washing up bowl will stain with sauces. It really is a MATter of of common sense. The mats are great and do the job they're supposed to.