Line a baking tray with greaseproof or baking paper.
Measure out your coconut, then split between small china or glass bowls in as many colours as you would like to use. I used four colours; yellow, red, blue and green, so I put 20g of coconut in each bowl.
Add a small amount of food colouring to each bowl of coconut. Stir well with a small spoon until the colour is completely mixed in.
If you're using gel or powdered food colourings, you'll need to add a splash of water to each bowl to help the colouring coat the coconut. Try adding one teaspoon of water, then add another if you're still struggling.
Add more colouring if wanted, until your coconut is coloured to the required shades.
Once you have coloured all of your coconut, tip it onto the lined baking tray and spread out into one layer. Try to keep the colours separate whilst they are still wet to avoid mixing.
Leave the tray out somewhere cool and dry, at a minimum overnight or for up to 24 hours until the coconut has completely dried. You may need to give it a little stir once or twice to ensure that all of the coconut gets a chance to dry out.
Once the coconut is dry, you can mix the colours together. We mixed ours on the tray, then tipped the sprinkles into a small tupperware box.
Store the dried sprinkles in an air-tight container until ready to use. Make sure they are completely dry if you want them to last - you can leave the lid off for a few more hours if you're not sure they are quite ready when you decant them.