Hue refers to the dominant spectral wavelength of light (red, yellow, green, blue, etc.). The symbol for hue is the letter abbreviation of the color preceded by a number from 0 to 10. With the YR (yellow red) range, the hue becomes more yellow and less red as the number increases. The notation for hue in the Munsell Color Book is located at the top right corners of the color chart page.
