My other half asked me to dye his jeans back to blue again (that shows our age), so I bought some hot-water dye and did the job. When I took the jeans out of the dye, I gathered some assorted bits of fabric and a pale peach t-shirt, left to recycle in some way due to - what? Couldn't find stains, no apparent holes from cat claws, so anyway I put it in the dye and didn't move anything around so I could get some random effects. I knew it would be pale because most of the dye molecules would have gone into the jeans (everything was cotton). After an hour, I rinsed everything out. The odd bits of fabric were actually quite dark blue but the t-shirt was light, with terrific tie-dye effects, couldn't have got this effect if I'd tried. Even the back came out great.