DIAGNOSIS That's called color uniformity or tinting, often visible as 'backlight bleed' or 'IPS glow' that isn't perfectly even. On a factory-calibrated monitor like the ProArt, it's more noticeable, but some degree is inherent to IPS panels. A severe tint on one side, however, can indicate panel stress.
FIX First, run a simple test. Display a full-screen mid-gray image (you can find these online). In a dim room, look at the screen from a normal viewing distance, dead center. If the tint is very slight and only visible from extreme angles, that's typical IPS glow. If it's pronounced straight-on, try gently massaging the affected corner or edge of the bezel with your thumb. Sometimes the panel can be slightly pinched by the frame during assembly or shipping. Apply light pressure on the bezel, not the screen itself.
IF THAT DIDN'T WORK Check if the issue changes when you adjust the monitor's tilt or swivel. If it does, it's likely pressure-related. Loosen the stand's tilt tension (if adjustable) so the monitor isn't fighting its own position. Also, ensure the monitor isn't overheating; poor ventilation can affect performance.
HEADS UP Color uniformity is a key spec for pro monitors. If the tint is strong enough to distract you during color-graded work, and it doesn't improve, use ASUS's warranty. They have tighter tolerances for ProArt models, and a clearly uneven panel should be considered for replacement, especially early in ownership.