Melting ice and food colouring with salt and warm water

I added a few drops of food colouring to a container filled with water and set it outside to freeze.  Three days later (yay, warm weather), I brought it back inside and stuck it in the freezer and 2 hours later we had a chunk of ice with an odd coloured middle.  Apparently, food colouring separates when you freeze it, who knew?  I put it in a tray, added some warm water, and gave Nate and Riley a spoon and some kosher salt and the very exact instructions "Lets see what happens when....."