What phenomenon occurs in color harmony where the eye notes the complement of a color just seen?

The phenomenon described is known as an after-image. This occurs when the eye perceives a color and then, when looking away or at a different surface, a perception of the complementary color is noted. This happens due to the way our visual system processes color; photoreceptors in the retina adapt to the presence of a specific color, and when that stimulus is removed, the brain can still "see" the opposite color for a brief moment.

This phenomenon is particularly strong when bright colors are viewed, resulting in a lingering perception of the complementary color due to the fatigue of the photoreceptors. For example, if one stares at a bright red object for an extended period and then looks at a white surface, a green after-image may appear, which is the complement of red.

Understanding after-images is important in color theory and design, as it influences how colors interact with one another within a composition, making it a key concept in creating visually appealing arrangements in floral design and beyond.