Hi Bob,

Near as I can tell, card table felt is the same as is used on pool tables. Water and a mild soap with gentle pressure using a soft cloth will get most of the spill out of the felt, but I don't know of any way to completely remove any colored stain from this type of surface. If the discoloration is just wear that might be "gunk" left from dirty chips, the same technique would be worth a try.

Bob