The monitor’s color gamut coincides with the standard sRGB color space in blues only. The P221W is much better than sRGB in reds and greens. The monitor uses backlight lamps with improved phosphors, hence the result.
Thus, in order to ensure accurate color reproduction, you should install the monitor’s ICC profile (you can find one on the included disc or create with a calibrator) and use ICC-supporting software.
The monitor’s sRGB mode (available in the color temperature settings) is expected to bring the color gamut into compliance with the sRGB standard:
As you can see, this option affects greens but leaves reds as saturated as before.
The gamma curves are somewhat higher than the theoretical curve for gamma 2.2, making the image somewhat brighter than necessary.
The gamma value gets even lower when the Brightness and Contrast settings are reduced.
The sRGB mode is not set up neatly, either. The value of gamma is too low, and the image is somewhat whitish. Moreover, the green curve has a distorted shape in the right part of the diagram. As has been shown above, it is the green point that is shifted in the monitor’s color gamut when in sRGB mode.
Thus, the P221W has good but not ideal gamma setup. It makes sense to calibrate the monitor additionally with a colorimeter. If you don’t distinguish between darkest halftones when looking directly at the screen after such calibration, try increasing the level of black a little in the monitor’s menu.