Place the blueberries in a bowl.

Add the boiling water and vinegar, stirring to combine.

Allow to cool for about 10 minutes, strain the dye, then add 3-4 freshly-cooked hard-boiled eggs.

Place the bowl in the refrigerator; leave eggs in the dye for as little as 1 hour or as many as 12, until desired color hue is achieved.

Remove eggs from the dye with a slotted spoon and place on a rack in the fridge to dry.