Preheat oven to 325 degrees.

Spray non-stick donut pan (6 donut size) with cooking spray and set aside.

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

In a smaller bowl, whisk together the yogurt, milk, egg, vanilla and melted butter.

Make a well in the dry ingredient bowl and pour the wet ingredients into the center.

Using a spatula, stir gently until no flour streaks remain. It is a thick batter.

Scoop two tablespoons of batter into each donut well and spread evenly.

Bake on center rack of oven for 12 - 13 minutes, until donuts feel springy when touched.

Allow to cool in pans for 10 minutes, then remove to cooling rack.

In a glass bowl, microwave the milk for about 15 - 20 second. Remove, add powdered sugar and whisk until completely smooth. Divide glaze evenly among five bowls (about 1/4 cup glaze in each).

Color the glaze: one blue, one black, one red, one yellow and one green.

Dip cooled donuts in glaze. Return to wire rack to dry.

Serve and celebrate!