DIAGNOSIS The HDR mode is likely active while you are viewing SDR content. The VG27AQ1A's HDR implementation can cause this desaturated, grayish look in Windows.
FIX Press the monitor's joystick to open the OSD. Navigate to Image > HDR. Set it to Off. Then, on your Windows PC, go to Settings > System > Display > HDR. Ensure "Use HDR" is toggled Off. For standard SDR use, set the OSD's GameVisual mode to Racing or sRGB for more accurate saturation.
IF THAT DIDN'T WORK The monitor may be in a low blue light mode. Check the OSD under Color > Blue Light Filter. Set it to Level 0. Also, ensure Shadow Boost is not set too high (GamePlus > Shadow Boost), as it can flatten contrast.
HEADS UP The monitor's default overdrive setting (Trace Free) at 80 can cause slight corona artifacts. For clearest motion, set Trace Free to 60 in the OSD under Image.