To make a frosting that will stand up to warmer weather, use 1/2 cup butter and 1 1/2 cups shortening.
If frosting is too thick, stir in a bit more milk. Just add a little at a time.
Coloring can be added after frosting is made. Just stir in amount of coloring you desire.
Keep left over frosting covered in fridge for up to a week. Bring to room temperature and stir before using.