Place the eggs in a single layer in a saucepan and cover them with water by at least an inch. Bring the water to a full boil, then remove the pan from the heat, cover it with a lid, and let the eggs sit for about 10 to 12 minutes. Immediately transfer the eggs to a bowl of ice water to stop the cooking process and make them easier to peel.
Once the eggs are completely cool, gently crack the shells and peel them under cold running water. Carefully slice each egg in half lengthwise. Remove the yellow yolks and place them in a small mixing bowl, then set the empty egg white halves aside on a serving plate.
Mash the egg yolks with a fork until they are smooth and crumble-free. Add the mayonnaise, yellow mustard, white vinegar, salt, and pepper. Mix until the texture is creamy. Add the green food coloring one drop at a time, stirring well after each addition until you reach a bright Grinch-like green shade.
Take your red bell pepper and wash it thoroughly. Using a small paring knife or a very small heart-shaped fondant cutter, cut out 12 tiny hearts. These will represent the Grinch’s heart that was famously two sizes too small before it grew at the end of the story.
Spoon the green yolk mixture into a piping bag fitted with a star tip, or simply use a plastic storage bag with the corner snipped off. Pipe the filling generously into the center of each egg white half. Carefully place one red pepper heart on top of the green filling and add a tiny piece of parsley if you want a bit more greenery.
