Depending on how many of these you make, you might need to repeat this a few times - we made two colours each time, by splitting the mix in half.
You will need: vinegar, and ice cube tray, food colouring, 1 cup of baking soda. 1/4 cup of water, 1 tsp of clear gelatine.
Mix the powdered gelatine and baking soda together. If you are making two colours, split the water in two containers. Now mix the food colouring with the water (if you use gel food colourings its much easier to use warm water - but make sure it has cooled before you do the next steps!). Once the colour mix is ready, add the baking soda and gelatine powder and give it a good mix. Pop the mix into an ice cube tray and freeze over night.
Once you have made all the colours you want, pop them into a tray and pour a little vinegar on top (using a pipette or old call syringe makes sure qualities don't get out of control and is also great for fine motor skills! Enjoy!