Based on the video context provided, the color of the Mepps Aglia spinner that is most effective for catching perch would be the perch pattern. The perch pattern typically consists of a black back, chartreuse side, and some type of flat or metallic shad finish. This color pattern is known to mimic the appearance of a perch, which is a common forage for bass. It is mentioned in the video that the perch pattern is effective in areas with heavy fishing pressure and can be used to catch bass in various water conditions across the country.
However, it's important to note that the effectiveness of a specific color can vary depending on factors such as water clarity, weather conditions, and the preferences of the fish on a given day. It's always a good idea to have a variety of colors in your tackle box and experiment with different colors to see what works best in your specific fishing situation.