If you are going to make two colours like we did, set out two large mixing bowls.
Add 3 cups of Epsom salts to each bowl, then 3 cups of rock salt and mix.
To each bowl add 4 -5 drops of food colouring and stir well with a large spoon.
Add 6-8 drops of Peppermint oil to each bowl and mix again.
Package the bath salts as you like! We used small cellophane bags and added ¼ cup of bath salts to each bag. This made 22 bags and 2 jars for her teachers.
Recipe by Planning With Kids at https://planningwithkids.com/2014/12/06/diy-peppermint-bath-salts/