Using foam boards is the smartest way to test your colors. Foam boards enable to get truer color comparisons because you can use them to see how different colors look in the exact same spot. If you paint directly on your wall, the color samples you create have to be in different spots. You want to be able to compare colors in the same spot. With boards, you can also move your color samples around the room to see how they look in different areas. This is important because your lighting is different around the room. And finally, with boards you just put them away when you are done evaluating your colors. You won't have unslightly swaths of paint on your walls for weeks while you either decide on your color or wait until you have time to actually paint. Each foam board is 12-inches by 10-inches by 1/4-inch.