[adrian_b]

I use a pair of Dell monitors with IPS screens (U2720Q and UP2414Q).

I always use as background a solid grey (#808080) and there is no noticeable non-uniformity.

I have tried now your color (#FF6400) on the U2720Q. Because this color is much brighter, if you look carefully you can see that there are small areas at the corners, especially at the 2 lower corners, with lower brightness. Also the 2 lateral edges have a slightly lower brightness, but the difference from the center is less visible than for the 2 lower corners.

However the areas affected are small (maybe a width of about 1/30 or 1/40 of the screen width) and you really have to look with the intention to find non-uniformities. When looking casually at the screen there is no obvious non-uniformity.

For emissive displays like CRT or OLED it is easier to achieve uniform brightness over the screen.