Combine the yeast, sugar, butter, and egg yolks in the bowl of an electric stand mixer fitted with a dough hook. Add the milk. With the mixer on low speed, beat for about 4 minutes to dissolve the yeast.

In a separate mixing bowl, combine the flour, salt, nutmeg, and lemon zest. Add to yeast mixture. Mix on low speed until it lightly comes togehter, then increase the speed to medium and beat until the mixture pulls away from the sides of the bowl, forms a ball, and climbs slightly up the dough hook. Remove the dough from the bowl, and generously oil the inside of the bowl. Return the dough to the bowl, turning several times to coat all sides with oil. Cover the bowl with plastic wrap, set in a warm, draft-frree place, and let rise until dough has doubled in size, about 2 hours.

Preheat oven to 350˚F.

Turn the dough out onto a floured surface and, using your hands, roll out into a 30-inch long cylinder. Place dough onto a greased baking sheet and bring ends together to form a ring, pinching together to seal. Place a well-greased 2 pound coffee can or shortening can in the center of the ring to maintain the shape during baking. Cover the ring with a towel and place in a warm, draft free place. Let the dough rise for about 45 minutes or until it doubles in size. With a sharp knife, make several slits around the top of the ring. Place in the oven and bake for 30 minutes, or until golden brown. After baking remove the coffee can immediately and allow the cake to cool.

Meanwhile, divide powdered sugar between three small bowls. Add green food coloring to one, purple to another, and yellow to the last bowl. Add 1 teaspoon of milk to each bowl and stir throroughly. You want a glaze that is not too thin, but not too thick to drizzle. Add more milk a few drops at a time to achieve the proper consistency.

After the cake has cooled to room temperature, drizzle with each of the colored glazes. Slice and serve.