S.K.
I have dyed shirts several times. I got the truest color with a big pot on the stove using rit dye. Boiling water and using a bucket, I got a very faded color. Be sure to add salt like the directions recommend. You can get on the Rit dye website and read the directions. They are easier to read than the tiny print on the box and they give you good tips. Also, I found the best selection of colors at Michaels but Walmart carries it too.
Good luck! Cute idea, BTW!