If you are trying to do the pastel shown in the picture you don't want to leave them in the dye for very long. Because the egg is very porous, they will take the dye very quickly!!! Give them a quick dunk in the water and very quickly pull them out to see if it is the color you want. Don't let them soak for long!!!!!
Remove the shells from the hard boiled eggs and slice each egg in half
Remove the yolks from the egg halves and place in a bowl. Set the yolks aside.
Get enough glasses or mugs for the number of colors you want to use. Fill the mugs or glasses 2/3 of the way full with cold water.
Add 3 drops of desired food coloring along with 1 tsp vinegar to each mug or cup.
Place egg whites in the mugs and allow to sit in the food coloring until desired color is reached. I could fit 3 egg whites in each of my mugs at a tim
Remove whites from dye and drain on a plate lined with a couple of paper towels.
Take the reserved yolks and mash them with a fork. Then mix in the 1/2 cup mayonnaise with the mashed yolk.
Pipe or spoon the yolk mix into the colored egg whites.