I got this idea from someone online. I don't remember who, when, or where. I totally forgot about it until last week, when I sat down and took inventory of my paint collection. Shook each bottle, inspected it, and painted the bottle's cap. It has really helped me see the difference between colors, intensity, and sheen. Here is a quick shot of some of my craft paint collection. I also own a number of Vallejo, Reaper, and P3 paints. I did the same with those, but they're not shown here. Give this little trick a try. You won't regret it.