Why is yellow a warning color?

Yellow is a warning color because it stands out against most backgrounds and is highly visible in both daylight and low-light conditions. The human eye is evolved to be most sensitive to yellow-green light due to the properties of the cone cells in our retinas. This makes yellow particularly salient and attention-grabbing relative to other colors, making it useful for conveying caution and danger. Additionally, yellow has been culturally associated with warning and caution for centuries, reinforcing its status as a universal signal for potential hazards.