Windows 10
Settings -> Personalization -> Background (should be where you landed on Personalization) -> Color Filters -> Use color filter: On (Optional: check box  to select shortcut key) -> grayscale (or other)

Windows 11
Settings -> Accessibility -> Color filters -> Color filters: On -> Grayscale (Optional: check box  to select shortcut key)

Color is used by designers to get your attention. Red, especially, being the color of blood, draws your eye. Color can be especially distracting for those with ADHD.