Choose either the same paint color for both levels of the home or colors that correspond with one another. Paint chip samples have colors in complementary tones, so you can pick two that you like from the same palette and be sure that they will work together. Choose neutral colors for a simple feel or more dramatic colors for a distinctive look.
Mark the place where you wish to change colors with painter's tape in a straight horizontal line. If there is a distinctive break in the two floors, skip this step.
Lay drop cloths on the floors where you will be painting the walls to avoid drips and spills. Use painting tape to cover baseboards and the ceiling so that you do not get paint where it is not wanted.
Place the paint into a roller tray. Use a roller to paint the majority of the walls in smooth, even strokes. Go over each area twice to make sure there are no drips. Use a large paint brush to paint the more difficult areas, such as corners, near the ceiling, and near the floor or baseboards.
Allow the paint to dry and paint additional coats as needed.