poster board and paint it the color you are thinking about. You can move the poster board around the room to see what it looks like in different lighting. Also, if you paint samples on the wall you are liable to paint it gloppier than a painter would. When you try and paint on top of a sample it is raised
poster board trick?! I am in the process of picking out a paint color for our Master Bath. I'm surprised the paint color in this picture has a gray name when it looks so blue in the photo.