Had a new bathroom put in with a new vinyl floor put down. It's standard black and white checkered pattern. Somehow my plumber got a smear of some expanding foam onto one of the white squares of the new vinyl flooring..! A bit of very tentative elbow grease managed to get it off, but now there is a noticeable patch. 
tinypic.com/r/3451kl4/9
Looking closely the vinyl surface seems undamaged, the fine stippling is there, no scratches or hazing. No trace of the foam left. But I can't get rid of this patch with bleach or owt. I'm assuming some top coat has been taken off the vinyl surface, does anyone have any suggestions? Is there such a thing as dye or chemical treatment for vinyl flooring or something along those lines?
Many thanks in advance for any help!