A buddy of mine with his brand new boat, and brand new sterns seat cushion (throwable life preserver) left it on a bow cushion, and it got wet.
Next day we noticed a big blue square, with a sterns logo in it. Not good.
We tried all the normal stuff. Water, soap, rubbing alcohol, bleach, 409, etc. It didn't budge.
Then I remember my fiance had bought a vinyl cleaner for our pontoon. Tried it, and it literally came off in 1 min. I was blown away. Like one of those infomericals.