Final answer:
A monochromatic color scheme consists of varying shades and tints of a single color. Option b. Green, blue-green, blue is an example of a monochromatic color scheme.
Step-by-step explanation:
A monochromatic color scheme consists of different shades and tints of a single color. In this case, option b. Green, blue-green, blue is considered a monochromatic color scheme as it uses varying shades and tints of the color green. The other options include multiple colors, which do not fit the definition of a monochromatic scheme.
Learn more about Monochromatic color schemes