Viewsonic have never approached us regarding calibration, so consequently we know nothing about their displays or calibration capability.
However, with a stated factory calibration of <2 dE, and with a 6-Axis Color Enhancement capability, I would not expect much colour accuracy capability.
(No display should ever have 6 axis colour controls, as secondary colour accuracy is always a direct result of primary colour calibration, unless the display has serious underlying issues.)
It would also appear the Viewsonic calibration software is just re-badged X-Rite, and is therefore not 3D LUT based.
(It appears to be basic Graphics card/ICC based, as is X-Rite's software.)
But, we would be happy to discuss accurate calibration with Viewsonic, if they would like to contact us.
Mob Boss at Light Illusion