Blue is a primary color that is often associated with the sky and the ocean. It is one of the three primary colors in the RGB color model, along with red and green. Blue can vary in shade, ranging from light hues like sky blue to darker tones such as navy blue. In color psychology, blue is commonly linked to feelings of calmness and tranquility. It is frequently used in design and art to evoke a sense of peace. Additionally, blue is a popular color in nature, found in many flowers, birds, and bodies of water, contributing to its widespread appeal.