Add your dye ingredient of choice to a saucepan (the size of the saucepan will depend on the number of eggs you want to dye that colour). Add the eggs and cover the contents of the pan with water.
Use a different saucepan for each dye, of course! Cover the contents of the saucepan with water and boil gently for twenty minutes.
After 20 minutes, carefully remove the eggs from the pan and place them in a heatproof jug or jar. Cover the eggs with the liquid from the pan. Add a generous splash of vinegar to the liquid, about a tablespoon per cup. Allow to cool and sit at room temperature for 4 hours or overnight (the longer you let them sit, the more intense the colour).
Remove the eggs from the dye and allow to dry. Once dry, you can rub the eggs with a drop of oil to intensify the colour, if desired.