I bought an outdoor sectional last year and after 1 year, the off-white cushions are badly stained from trees, leaves, etc. I tried washing them in my washing machine using various methods with no luck.

I was thinking of trying to dye them a dark gray. I haven't really found any dyes specifically for outdoors and was wondering if regular dyes would work.

The cushion covers are 100% cotton.

I saw fabric paint for outdoors, but it seemed very expensive.