Which one of the following is considered a cool color?

Blue is considered a cool color due to its association with calmness, tranquility, and often cooler temperatures. In the color wheel, colors are typically categorized as warm or cool based on their visual temperature. Cool colors, including blue, green, and purple, tend to evoke a sense of serenity and can be perceived as receding or creating distance. This makes them popular choices in various design and aesthetic applications, as they can create a soothing atmosphere.

In contrast, warm colors such as red, yellow, and even orange are perceived as more energizing and stimulating. They evoke warmth and can create feelings of excitement or urgency. Green, while it can have both warm and cool undertones depending on its shade, is generally considered a cool color when in its more bluish tones, but blue distinctly stands out as a pure cool color in this context.