I have white canvas on my boat. I leave the canvas on all summer at Belmont Harbor. My white canvas gets ugly every year. I found a product that works great for any colored canvas, especially white. It is a Mold & Mildew Stain Remover by a company called Iosso Products located right here in Elk Grove, IL. I rinsed off my dirty white canvas with my pressure washer, then I mixed some of the Iosso product with warm water and applied the mixture to the canvas with a soft brush And let it sit for about 10 minutes. Then I used my pressure washer to clean the dirt off. This got my canvas practically as clean as new.