mats
 

do plastic or rubber backed mats mark vinyl?

Yes, very often they will turn the sheet goods yellow----

Yes, it's called plasticizer migration. "This is caused when a plasticizer in a floor mat or floor material transfers itself (migrates) into the floor finish or sealer. This is responsible for the discoloration sometimes found around or under floor mats."

Natural Rubber is fine. Synthetic rubber is bad.