At the default settings the gamma curves for red and green are close to the theoretical curve for gamma 2.2, but the blue curve is sagging.
But when the Contrast setting is reduced, the curves smooth out and get closer to each other as well as to the theoretical curve (painted black in the diagram).
The ViewSonic VX2268wm offers five preset color temperature modes. The sRGB and 6500 modes are the most accurate ones. The temperature dispersion among the different grays is rather small, although green is slightly excessive. These modes differ from each other in that the 6500 mode makes all user settings available whereas the sRGB mode blocks the Contrast setting.
When I adjusted the monitor manually (in the User mode), I set Contrast at 50 and chose R=91, G=87 and B=100. You can see the result of my manipulations above: it is quite close to ideal.
As you can see from the table, the difference between the different grays is no bigger than 300K in the 6500 mode and with the manual setup. This is an excellent result for a home/gaming monitor.