In a stand mixer, beat the egg whites on medium until they turn frothy, about 1 to 2 minutes.
Lower the mixer speed to low and gradually add in the powdered sugar a little at a time.
Add in the vanilla.
OPTIONAL: If using food coloring: separate the icing into separate bowls and add a few drops of food coloring to each bowl, stirring until the color is even and adding more food coloring until you reach your desired color level.
Notes
Storage: you can store this royal icing in an airtight container in the refrigerator for up to two weeks.