Activating survival instincts

Some theories suggest that humans are naturally attuned to see red because it helped our ancestors survive. Human eyes have more cones that are sensitive to red and yellow wavelengths compared to blue.^[1] This helped early humans notice red signals that could indicate danger, like poisonous animals or plants, or benefits, like ripe fruits​.^[2]

In design, red often serves to warn users or signal a stop, like indicating an error or a destructive action such as deleting an account. The instinct to notice red can also make users act quickly, as it creates a sense of urgency.