There are recipes for colored rice all over the web. I’ve seen some that involve cooking the rice on a pan in the oven and even tried one that used rubbing alcohol to speed up the drying time. I like the recipe below because it is no-cook and is toddler safe, as it uses vinegar to set the color. Adjust the measurements as needed to make more or less rice.
Pour half a cup of white rice into a metal mixing bowl.
In another small metal or glass bowl, combine one tsp of vinegar with several drops of food coloring.
Add the food coloring to the rice and mix until all the rice is colored.
Spread the rice onto a sheet of parchment paper and let air dry.
Tips: Instead of a bowl you can use separate freezer bags to mix each color. Look for plain white rice at a bulk store. Keep it in a closed container to use again and again.