Place eggs into a large pot and fill with cool water, covering eggs about ½ inch.
Bring to a boil and boil for 5 minutes.
Cover, turn off the heat, and let sit for 10 minutes.
Remove eggs from the pot and place them in a bowl in the sink and let cool water run over them for about a minute then let them sit in the bowl.
Once cool enough to handle (they don’t have to be completely cooled). Use the handle of a dull butter knife to crack all around the shell of each egg.
Re-heat the water used to boil the egg until it begins to steam (not boil).
Add water to a large bowl.
Scoop out some black food coloring gel with the knife and mix it around. (Used about 3 scoops of the size shown in the pic.)
Mix and swirl around into water to dissolve and color the water.
Place eggs into the dyed water and let sit for 20 minutes. (If the water isn’t covering some of the eggs, just go back and move around to get all sides.)
Take the eggs out of the dye and run them under cool water to remove the remaining dye.
Carefully remove the shell and place de-shelled eggs to the side.
Cut each egg lengthwise, placing the yolks into a medium bowl.
In the bowl with the yolks, add mayo, mustard, garlic, pepper, and salt.
Use the back of a fork to mash the yolks and mix to combine.
Use a knife to scoop a little bit of violet food coloring and dip it into the yolk mixture and mix until completely combined.
Place into a ziplock bag and cut off one end. Fill each egg halves where you removed the yolk, with the mixture.