I have a zip up Reebok hoodie in a beautiful rich blue, or at least I do now!! Due to years of washing it had begun to look tired, old and faded, but after using the dye it looks brand new again.
I have used these dyes for years so know they work, but I have mainly used black ones to re-dye my trousers which get bleach splatters on them from work. It says on the box that they don't cover bleach stains - well I've never had any difficulty doing so, but the trousers I dye are 100% cotton so that probably is the reason why. The dyes only work on cotton based material so don't work on completely manmade fibres like nylon and polyester and if you have a mix of cotton and Polyester the shade isn't as vibrant, which is also factor to consider when dying something as the stitching on some clothing can be done with polyester thread and you can end up with an interesting stitched effect where the stitching is a different shade where the dye has not touched it. They don't affect other washes as long as you follow the instructions on how to clear your machine afterwards, and I always go round the seal of the washing machine with a piece of kitchen towel to remove residue. You don't have to use the special dye salt either any common cooking/table salt works just as well.
I would recommend these dyes to anyone as, for the cost you pay can refresh your wardrobe for a fraction of the cost it would be to replace the clothes.