Place an empty paint can on the covered workspace or outdoor space such as grass.
Fill three-quarters of the paint can with white base ceiling paint.
Dip a teaspoon into the black ceiling paint -- or any other color of darker ceiling paint -- and add 1 teaspoon of darker-hued paint. You can always apply more color, not less. So add the darker paint 1 teaspoon at a time.
Mix the paint thoroughly with a paint stick, churning it until all of the dark paint is blended into the white paint.