I have a Dell XPS L502x laptop and two LG IPS235 monitors. One of them connected through HDMI-HDMI, another through Mini DisplayPort - HDMI.
Although these are the same monitors, if I set them to default settings, the calibration is absolutely different. The default settings of the monitor, that is connected to GeForce GT 540M through HDMI - HDMI are very bad - the white is like yellow and the black is like gray. I tried to change that using the keys on the monitor and NVIDIA Control Panel, but I couldn't achieve the same result, as the other monitor.
Here is the screen shot of my NVIDIA Control Panel: Monitor 2 is connected through Mini DisplayPort - HDMI, Monitor 3 is connected through HDMI - HDMI.