Wasn't your detergent. Bet you washed them in hot water which is no no. You can dye them regular dye and it will work fine. Just remember, and any dry cleaner will tell you, hot water are clothes worst enemy.

Used a cheap laundry detergent and it faded all of my knit yoga pants - now they are more like a dark gray and look horrible even though they are only worn lightly - they are decent quality -LL Bean. Has anyone successfully dyed knits black? Any special hints? I hate to toss them but they look horrible. Thanks.As a reference I switched from Cheer Free to All Small and Mighty - wash everything in cold water except sheets.

Used a cheap laundry detergent and it faded all of my knit yoga pants - now they are more like a dark gray and look horrible even though they are only worn lightly - they are decent quality -LL Bean.