Mask off a dividing line between the areas that are to be painted with different colors. Tape a piece of masking tape on the edges of the area you will be painting. You can mask a room horizontally or vertically.
Lay tarp over the floor to protect it during the painting process. Secure the tarp with tape.
Pour the first paint color into a roller tray. Dip the paint roller into the paint and roll off any excess paint.
Paint the area within the masking tape with the roller in long strokes. Make sure that you paint in one direction only to avoid streaks on the wall. Let the paint dry for six to 12 hours.
Remove the masking tape and apply new tape along the interior edges of the newly painted area of the wall.
Pour the second paint color into a different rolling tray. Dip a clean roller into the paint. Then paint the second area with the second paint color.
Allow the second area to dry for six to 12 hours. Once dry, very slowly and gently remove the masking tape.
Touch up any rough edges with a very fine paintbrush and let these touch-ups dry as well.
Apply a clear topcoat to the entire wall and let it dry overnight.