A color scheme is considered the colors used in various artistic and design contexts throughout the concept of color theory. For example, the achromatic system uses black text with a white background and is an example of a fundamental and common default color scheme in web design. Another color scheme example could be a 4 color, tetradic color combination. In simple terms, a color scheme in CSS is a combination of colors used to make a theme of a website or page using CSS styles and properties.