DIAGNOSIS The default out-of-box picture profile is likely set to a less vibrant mode, or the GPU output is mismatched.
FIX First, open the OSD with the joystick and go to 'Color Adjust'. Change the 'Color Temperature' from 'User' or 'Bluish' to 'Warm' or 'sRGB' for more accurate, richer colors. Then, ensure 'Gamma' is set to '2.2'.
IF THAT DIDN'T WORK Check your graphics card control panel (NVIDIA Control Panel or AMD Adrenalin). Under 'Change resolution', confirm the output color format is set to 'RGB' (not YCbCr) and output dynamic range is set to 'Full' (not Limited).
HEADS UP The 'Game Mode' setting can override your color adjustments. If you enable it, go into its sub-menu and verify the color settings there as well.