Kool-Aid and other drink mixes can be used as an acid dye in a much more complicated hot-water and vinegar process intended for protein fibers (such as wool) but as a cold water dye for cellulose fibers (like cotton), it simply doesn't have the staying power.
Kool-Aid will only work properly if you are using a hot water technique to dye protein fibers. Try this tutorial from Sarah E. White on dying wool with Kool-Aid.
For cellulose fibers such as cotton, rayon and linen, don't use Kool Aid as a cold water shortcut. My advice is to do it the right way, first, using fiber reactive dyes instead. More Questions About Dyeing Clothing
Protein (Wool, Cashmere, Silk)
- What are Protein Fibers?
- How to Dye Protein Fibers
- Learn about Acid Dyes
Cellulose (Cotton, Linen, Hemp)
- What are Cellulose Fibers?
- How to Dye Cellulose Fibers
- Learn about Fiber Reactive Dye