In large mixing bowl put hot water, food coloring and vinegar and whisk until blended well.
Add unpeeled eggs to water mixture making sure it covers eggs completely (add more hot water, if necessary).
Allow eggs to stand in colored water for 30 minutes. With slotted spoon, remove eggs, dry and peel. Slice eggs in half lengthwise. Carefully remove yolks from eggs and place in small bowl. Place egg whites on a platter.
Coarsely mash egg yolks with a fork. Add mayonnaise and mustard and stir until well combined. Stir in onion and cilantro. Spoon yolk mixture into each of the egg whites. Press a slice of olive into the egg yolk mixture then add a dab of ketchup to finish off the eye. (Pimento stuffed green olive slices work in place of ketchup and black olives.) Cover and place in refrigerator until you are ready to serve. They have the best bloodshot effect if served within 2 hours of preparation. Makes 1 dozen.