I bought from charity a Karrimor Alpiniste 'sac a while back and it needs a bit of work doing - it's lost a few seams and is filthy for one, but it's the colour I have the most objections to... purple just isn't all that cool. Don't call me vain, but it just doesn't go with my orange Superfly!

Is it possible to dye a thick rucksack material to the extent it will last, not run even if in blizzards or rain, fade to a minimal extent and not damage anything it comes into contact with? Black would seem an obvious colour to dye it to. Any advice, suggestions, or step-by-step instructions would be much appreciated.

There is a discussion on this very topic her. 

http://www.outdoorsmagic.com/forum/forummessages/mps/dt/4/utn/16837/last/1/V/1/SP/