Beat the room-temperature butter in a stand mixer with the paddle attachment or with an electric mixer by hand. Beat on medium speed until light and a fluffy consistency.
Slowly add in powdered sugar and beat as your adding.
Beat until it is fully mixed in.
Add in vanilla and milk or heavy cream beating for 1-2 minutes until smooth. If it's too thick, add a splash of heavy cream or milk until you reach the right consistency that you want.
Divide cups of frosting into separate bowls and add in different colors of food coloring if desired. There are different brands of natural food coloring but I like to use the Watkins brand. They are dye free and colored using nature. Sometimes I will also use different foods like beet root powder for red, dehydrated spinach or kale blended into a powder for green, and turmeric for yellow. Get creative on how you color your frosting!
Use the fluffy frosting to frost cooled cupcakes, cakes, or cookies.
Notes
If you want to make this a chocolate frosting, simply add in 1/4 cup of cocoa powder with your powdered sugar and mix to combine before adding it into the beaten butter.