I froze a bowlful of water a few weeks ago in anticipation of this project. We finally found time to do it, so I dumped the ice onto a tray and gave the girls a container of salt and food coloring.
They poured on the salt and squeezed on the food coloring.
Last time we did this project was when O(5) was 2 or 3 years old. She was SO proud of her beautiful ice that we had to keep it in the freezer for months! Luckily, they didn't ask to keep their beautiful ice this time (because we don't have any room in our freezer)!