The correct answer is "monochromatic". When only a single color with different values (lightness and darkness) is used to create an artwork, it is referred to as a monochromatic color scheme. Monochromatic artworks typically have a unified and harmonious aesthetic, as they involve variations of a single color. To find this answer, you can either have prior knowledge about color schemes or you can do a quick search online using keywords such as "artwork with a single color" or "monochromatic color scheme." This will lead you to resources that explain the concept and provide the correct answer.