Grease and flour a silicone or regular bundt pan. If using a silicone bundt cake, place it on top of a baking sheet pan.
In the bowl of a mixer, beat together granulated sugar and butter, stop once to scrape the sides and bottom of the bowl.
Add eggs one at a time and beat on medium speed until well blended.
Change speed to low and add milk and peach extract. Increase speed back to medium and mix well. Add flour, baking powder, and salt and beat about 1 minute or until smooth. Stop once to scrape the sides and bottom of the bowl.
Divide batter into 4 bowls and stir in gel food color with a spatula until well combined.
Add the colored batter into the prepared pan, start with red followed by yellow, blue and purple.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
Let cake cool into the pan on a wire rack for 10-15 minutes. Gently loosen cake from pan and turn out onto wire rack; cool completely before icing.
Add powder sugar, 3 tablespoons milk and peach or vanilla extract into a medium bowl and mix until fully incorporated and smooth. If the glaze is not runny enough, add more milk. You need the glaze to be thick enough to hold it's "drip" on the cake, but runny enough to pour.
Pour glaze over the cake and immediately decorate with sprinkles.
Let the glaze completely settle. Slice and serve the cake.