DIAGNOSIS It's probably running in a limited color range (16-235) instead of the full range (0-255) that your PC expects, which crushes blacks and washes out colors. This is a common handshake issue, especially with certain GPUs.
FIX On the monitor itself, press the joystick to open the OSD. Go to 'Color Setup' and make sure 'Color Temp.' is set to 'Normal' or 'sRGB' to start. Now, on your PC: if you have an NVIDIA GPU, open the NVIDIA Control Panel, go to 'Change resolution', scroll down, and set 'Output dynamic range' to 'Full'. For AMD Radeon software, it's under Display > Pixel Format > Full RGB.
IF THAT DIDN'T WORK The monitor might be stuck in a non-gaming preset. In the OSD, go to 'Game Setting' > 'Game Color' and bump that up to 12-15. Also, under 'Extra', make sure 'DCR' (Dynamic Contrast Ratio) is 'Off'. DCR can make things look really weird and artificial.
HEADS UP The out-of-box default response time setting can also make colors look a bit off. Don't confuse the 'Response Time' setting (for ghosting) with the 'Overdrive' setting—they're the same menu. 'Medium' is the recommended balance.