Final answer:
Simultaneous contrast refers to the visual tension and heightened vibrancy that occurs when complementary colors are placed next to one another, as seen in the works of artists like Keith Haring and Caravaggio.
Step-by-step explanation:
Simultaneous contrast is an intriguing aspect of color theory in the visual arts, which is particularly relevant when discussing the interaction of complementary colors. For instance, when gray is placed on a red background, it appears slightly greenish because our eyes try to balance the color spectrum by shifting the neutral color towards the complement of the surrounding color. Furthermore, when a non-dominant color is presented next to a dominant one, it appears to move towards the dominant color's complement. Not only does color interaction affect the hue, but it also affects the perceived values, making colors seem darker when placed next to lighter shades, and vice versa.
The high visual contrast associated with complementary colors is clearly evident in the example provided by the work of Keith Haring. When blue and orange, which are complementary, are placed adjacent to each other, they appear more vibrant and suggest a sense of action or tension. Artworks such as Caravaggio's Judith Beheading Holofernes exploit this concept by using high contrast to heighten the drama of the scene. Similarly, the Impressionist technique of painting with small strokes of pure color side by side was meant to allow the eye to mix these colors optically, resulting in a more vibrant visual effect when viewed from a distance.