Birds can also see ultraviolet light in the 300-400 nm range, and a bit into the red range, but not as far as humans.
Animals that can see the ultraviolet range, can not see red wavelengths.
The shorter the wavelength of the light, the more it is refracted. Violet or purple is the shorter wavelength of visible light. As the wavelengths get longer the visible light and frequency change in color to blue, green, yellow, orange, and red, which is the longest.
Colors of light travel at different speeds. Red travels the fastest, so it is on the top (least bent/ refracted). Red also has a long wavelength, but a low frequency. Violet travels the slowest, so it is on the bottom (most bent/refracted). However, violet, with its much sorter wavelength, has a higher frequency. Thus, violet provides the most energy and explains why blueberries and other purple/blue foods, rich in antioxidants, are so nourishing.
Warm colors (red, orange, and yellow) evoke feelings of happiness, optimism, and energy. However, too much orange and yellow can slightly irritate the eyes. Too much red can also irritate.