Layers of different coloured salt added to a transparent bottle make a decorative sandscape, providing you don't shake the bottle and turn it to muddy brown. You might also want coloured salt for culinary purposes. There are several ways to colour table salt. One method is not suitable for culinary purposes; use it in craft projects.
Craft coloured salt
Pour table salt into a plastic food storage bag, filling less than half the bag.
Add a piece of coloured chalk to the bag.
Seal the plastic bag.
Massage the bag, breaking up the chalk and blending it with the salt. The salt will take on the colour of the chalk, and the chalk will disappear into the salt. Add more chalk for a darker colour.
Culinary coloured salt
Pour salt into a bowl.
Add a drop of food colouring to the salt.
Stir the salt with the spoon, mixing in the food colouring with the salt. Add more food colouring if desired.
Spread the salt on a plate in a thin even layer. Allow it to thoroughly dry.