Seems the general consensus on cleaning playmats is dish soap and toothbrush, or dish soap and multiple soaks and line dry.
I own 2 3 foot by 3 footers and doing that with a toothbrush is not a fun idea. I normally throw them in the bathtub with dish soap and a baby hair brush and that works great for deep cleaning, but it's time consuming and takes forever to rinse out all the soap from it, and it's definitely a workout because of the size of my mats.
I found something great that works in a pinch and is quick to spot clean or to do a light clean before gaming. You will still have to deep clean from time to time but it really cuts down on that.
try some baby wipes. they are amazing. I notice slight off colorations when my mats get slightly dirty because my mats are black. The wipes take care of that in a few seconds. They also dry super fast as they are damp but not saturated in liquid.
I highly recommend them.
Baby wipes, safe for my baby's bum, safe for my playmats.