Screen displays wrong colors

Everything is grayscale, black and white

Go to Settings > Digital Wellbeing & parental controls > Bedtime mode > Customize > Screen options at bedtime and turn Grayscale off .

Everything is negative, reversed colors

Go to Settings > Accessibility > Color inversion and turn it off .

Tones, hues are different or missing

If the screen shows warmer tones than usual, check quick settings. If Night Light is on, turn it off.
If certain colors appear diminished or their hues are different, go to Settings > Accessibility > Color correction and turn Use color correction off .

Background turned dark/light

Go to Settings > Display and turn Dark theme off .