The document discusses how artificial light can affect the appearance of colors. It describes the three most common types of artificial lights - sodium, tungsten, and fluorescent - and how each can influence how colors are perceived. Sodium lights impart a yellow hue and can cause greens and blues to appear warmer. Tungsten lights also make colors seem warmer. Fluorescent lights have a slight blue-violet tint and can impact a color's overall appearance. The document stresses that different lighting conditions can cause a color to appear differently, so colors should be selected under the lighting in which they will be used.