The color of blue and yellow harmony is green. This is because when blue and yellow are mixed together, they create a secondary color known as green. This principle is based on the color wheel, which is a model that represents the relationships between colors. According to the color wheel, blue and yellow are primary colors that, when combined, produce green, which is a secondary color. This harmonious blend is widely recognized in art, design, and nature, as green is often associated with growth, harmony, and balance.

The reason for this color harmony lies in the way human eyes perceive light and color. When light from a blue object and light from a yellow object strike the same point on the retina, the brain interprets the combined light as green. This is due to the way the cones in the retina, which are responsible for color vision, respond to different wavelengths of light. Blue light is absorbed by the cones that are sensitive to blue wavelengths, while yellow light is absorbed by the cones that are sensitive to yellow wavelengths. When both types of light are present, the brain combines the signals from these cones to perceive the color green.

Data from color theory and color psychology support this explanation. For instance, the CIE 1931 color space, a standard model for color representation, includes green as a primary color. Additionally, studies in color psychology have shown that green is often associated with positive emotions and a sense of well-being. This is likely due to the fact that green is the color of nature, which is typically associated with tranquility and harmony.

In conclusion, the color of blue and yellow harmony is green, a secondary color that is created when these two primary colors are mixed. This harmonious blend is supported by the color wheel, the way human eyes perceive light and color, and scientific data from color theory and color psychology.