Add the vinegar and a bit of the food gel or food colouring. You won’t get colours that are as vibrant if you use food colouring as opposed to the gel. If you want to add essential oil, add 1-2 drops at this point.
Seal the bag and shake well until all the rice is coloured to your desired colour.
Spread the coloured rice out on a baking tray covered with aluminium foil or baking paper to dry overnight.
Repeat with other colours.
Use in sensory play.
Store in an airtight container or a large zip lock bag and keep it a dry place. As long as it is stored properly, it should last a very long time.