•  Preheat oven to 350 degrees F. Combine all ingredients, except for food coloring, in a large bowl and mix with an electric mixer until well combined.
• Divide cake batter evenly between six bowls. For each bowl add 1-2 drops of food coloring and mix. If more color is desired, add additional drops of food coloring until desired color is reached. Repeat with each bowl. 

  
  
  
• Generously spray a standard sized Bundt cake pan with non-stick cooking spray.   Starting with the red batter, spoon cake batter into bottom of Bundt pan. The cake batter should go around the bottom of the pan in a complete circle.

  
  
  
• Carefully spoon the orange cake batter into pan, placing it directly on the red cake batter, once again making sure it goes completely around the red cake batter. Try not to mix the different colored cake batters, simply spoon one on top of the other. Repeat with remaining colors in the following order: yellow, green, blue, purple.

  
  
  
• Place in oven and bake for 50-55 minutes or until toothpick inserted into cake comes out clean. Remove from oven and allow to cool in pan, on a wire rack, for approximately 10-15 minutes. Tap the pan firmly a few times on the countertop, gently shaking it to help loosen the cake. Carefully invert the pan onto a cake plate and lift the pan off of the cake. Allow the cake to cool completely prior to adding glaze.

Glaze

• Place powdered sugar and milk into a bowl and stir well to combine. Add vanilla and stir to combine. Glaze should be thin enough to spoon over cake, but not runny. If glaze is to thick, add additional milk, 1 teaspoon at a time, until a spoonable consistency is reached. 

  
  
  
• Spoon glaze over the top of cake. If desired, garnish with rainbow sprinkles.