Preheat the oven to 350 °F (175 °C). Grease and flour a loaf pan or line it with parchment paper.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, use an electric mixer to cream the softened butter and sugar until light and fluffy, about 3 to 4 minutes.
Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.
Add the blue gel food coloring gradually until your desired color is achieved, then mix in the milk until smooth.
Gradually add the dry ingredients to the wet mixture, folding gently until just combined to avoid overmixing.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 50 to 60 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10 to 15 minutes, then transfer to a wire rack to cool completely.
Dust with powdered sugar or drizzle with vanilla glaze if desired before serving.