Tone:In gemology, tone refers to the degree of lightness or darkness of a color. The tone of a color can range from very light (also called pale) to very dark (also called deep). The most important factor affecting tone is the amount of light that is reflected from the surface of the gemstone. The more light that is reflected, the lighter the tone will be; the less light that is reflected, the darker the tone will be. Tone can also be affected by other factors such as saturation (the purity or intensity of color) and hue (the basic color). (4)