1: Everything on the OSD are exactly the same. That's the very first thing I did obviously. Also, I did the memory recall (Memory Recall is on the OSD and resets the settings to factory settings). So even if I missed something on the first trial, the second one after memory recall still looked exactly the same.
2: Little? It's quite a bit. Ask everyone who looks at it. I use a Dual-Monitor (2560x1280) wallpaper and trust me it looks different. The left monitor has a sunset hue and the right monitor looks more like the weather in a storm just because they are a different color. Of course, I don't know which one is the correct one.
3: Center? It's the entire screen. Trust me. You can be far away from the monitors and notice that both look completely different colors.
Follow the instructions and adjust both screen at the same time step by step. This is mostly for brightness and contrast ratio. It will not help you with color accuracy though. For that you will have to manually tweak one of monitor's RGB settings in the OSD until you are satisfied. Then adjust the RGB settings of the other month until it visually matches as close as possible.