In a mixing bowl, mix 1 cup of boiling water with the blueberry gelatin, and stir the mixture until fully combined. Add ½ cup of cold water to the mixture and then stir. Then, chill the mixture by pouring it into a cake pan and then placing it into the fridge for one hour.
In another bowl, mix the condensed milk with 1 cup of boiling water. Then, take a pan and mix 1 cup of boiling water with grape gelatin. Then, fully combine the grape gelatin mix with the condensed milk mixture. Then, add ½ cup of cold water and mix thoroughly.
Take the cake pan out of the fridge and then pour the condensed milk mixture over the top of the blueberry gelatin layer and cool it inside the fridge for another hour.
In another bowl, combine 1 cup of boiling water with the raspberry gelatin. A, then add cold water (½ cup) to the gelatin and mix it properly. After chilling for one hour, take the cake out of the fridge and then pour the gelatin mixture over the condensed milk layer and chill it for three hours.
In another bowl, whip the heavy cream with vanilla extract and powdered sugar. When it is whipped properly, divide it into three equal parts and then mix the three food colorings.
After chilling, take the cake pan out and remove the cake from it. Now pipe the whipping cream in the piping bag. There should be three piping bags, one for each color.
Use your artistic mind and place the dollops of whipped cream to create a galaxy effect.
Sprinkle the glitter over the cream, if you want to give more depth to the cake.