Preheat the oven to 350°F and grease a donut pan.

In a large bowl, whisk together the flour, sugar, baking powder, and salt.

In another bowl, combine the milk, vegetable oil, eggs, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix until just combined.

Divide the batter into three bowls: leave one plain, add red food coloring to the second, and blue food coloring to the third.

Spoon the red batter into the donut pan, filling each cavity about one-third full.

Add a layer of plain batter on top, then finish with a layer of blue batter, filling the cavities about three-quarters full.

Bake for 10-12 minutes or until a toothpick inserted comes out clean.

Allow the donuts to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

In a small bowl, mix the powdered sugar and 2 tablespoons of milk until smooth to create the icing.

Dip the cooled donuts into the icing and decorate with sliced strawberries and blueberries to create an American flag design.