Take a bowl and add cocoa powder, all-purpose flour, baking soda, baking powder, milk powder. Sieve them 2 to 3 times and keep aside.
Take a small bowl and transfer milk into it. Add blue gel food color and mix it properly. Notes - I actually like this way as the color gets mixed properly.
Take a mixing bowl and using an electric mixer, whisk oil and powdered sugar together. Also, add vanilla essence.
Once the sugar and oil are mixed properly, add curd and flour mixture. Add gel food color mixture and whisk it at low speed for 2 minutes approx.
The batter is ready. Transfer your batter in a cupcake pan evenly.
Bake in a preheated oven at 180˚C for 15 minutes.
Check it with a toothpick.
Cool it down and decorate with buttercream.
Video
Notes
make sure your milk and oil both are at room temperature.
cocoa powder soaks the moisture so, before decorating, check the texture of the cupcake. If you feel a little bit of dryness, spread water using a spoon on the top of cupcakes.
you can achieve your desired color shade.
you can always adjust the consistency of the batter by adding tablespoons of water.