Rit dye is to fabric dye as Kleenex is to tissues. It's the quintessential cheap brand name. It's been around for 80 years and has very little competition. Chances are that if you've dyed or tie-dyed a garment, or some piece of cloth, you did it with Rit.
It comes in powdered and liquid forms and can be used on most porous materials. It's easy to find - most drug and discount stores carry it.
Some things to do with it:
- Get extra life out of your jeans by lightening or darkening them as fashion changes.
- Take a page from the Book of Mentos and pinstripe a suit by painting vertical stripes on it with bleach.
- If your socks and unmentionables get so old they turn grey, dye them a bright color. This is a life saver if you like to dress to display bra or thong straps.
- Get an old flannel and drip various colors on it. Now people will think you're an artist!
- Tie dye (if you must).
wertperch points out that the UK equivalent is something called a "Dylon".