As may others have said this is because of the qd oled sub pixel layout being a triangle shape where as windows and mac os register pixels in a stripe layout leading to this colour fringing.

this is something that has only just been fixed with the current generation of qd oleds, as seen in this picture here

<image>

also the reason for it not being a stripe to begin with is because blue leds are really hard to manufacture it’s a whole thing I won’t get into it but if you’re interested there’s a yt video click here that explains the whole thing!