Vacuum the rug thoroughly to remove all dust and debris. If particularly dirty, take the rug outside, hang it over a chair and beat the dust out of it with a broom.
Lay the rug flat on a drop cloth. A braided rug is porous and will allow the paint to seep through the fibers and ruin the floor underneath.
Determine a design. Start with a border. Measure 4 to 8 inches from the edge of the rug all around the perimeter. Mark the rug with chalk every 6 inches. Tape off the border with low-tack painter's tape. Use a thick tape to help prevent painting outside the tape line.
Paint the rug using a foam roller or a foam brush. Use a small amount of paint, continuing to add more until you get a depth of color that you like. Allow the border to dry completely and slowly remove the tape.
Evaluate your rug and determine additional designs. Use a stencil to add decorative elements to the rug in the same color or another complementary color.