Rainbow Cupcakes

Step 1
Preheat the oven to 350 degrees F (175 degrees C). Line two 12-cup muffin pans with paper baking cups.

Step 2
Stir together flour, baking powder, baking soda, and salt in a large bowl. Whisk together milk, vegetable oil, and vanilla in a separate bowl until evenly blended; set aside.

Step 3
Beat sugar and butter with an electric mixer in a large bowl until light and fluffy. The mixture should be noticeably lighter in color. Add eggs one at a time, allowing each egg to blend into the butter mixture before adding the next. Pour in the flour mixture alternately with the milk mixture, mixing until just incorporated.

Step 4
Divide cake batter into four separate bowls. Add a few drops of food coloring into one bowl of batter and stir; add more food coloring if necessary to reach the desired shade. Repeat with remaining colors and bowls of batter.

Step 5
Using a different spoon for each color batter, spoon a small portion of each color into the cupcake liners, until 1/2 to 3/4 full. Do not mix the batter once it is in the cupcake liner.

Step 6
Bake in the preheated oven until a toothpick inserted into a cupcake comes clean, 15 to 20 minutes.