About 5 days ago I attempted this for the first time on my GP extra 300S 60 size. Here's what I did.

Purchased 1 Black Rit Dye and 1 Navy Blue

Filled a 5 Gallon bucket with about 3 1/2 to 4 gallons of tap water as hot as it would come out of the tap.

Put both bags in

Added a couple cups of salt

Mixed 30 secons to 1 minute

Submerged My canopy

I frequently checked it, just pulled it out and looked at it if it was to light I put it back in. After about 15 to 20 minutes I achieved these results.

Good Luck.