I'm using my samsung galaxy s9 plus for 6 months of period. And it's all look very good before I recieved a software update end of the last month. The yellow tinted color problem appears when I press the power / lock screen button to lock the screen & immediately if I press the power/lock screen button to re-enter into the phone before ALWAYS ON DISPLAY appear, the screen turns to yellowish color. To return the phone display to the normal state, have to press the power/lock screen button & wait until the AOD comes.
That's the blue light filter. If you swipe down to the notifications screen, and then swipe down again you should be able to find th option to turn it off. It give a yellowish tinted to protect your eyes from the strain of your phone's screen. You can probably search it in settings and well by typing in Blue Light Filter.