同時対比

Simultaneous contrast was first systematically described by Michel Eugene Chevreul in 1839. A gray square on a red background appears slightly greenish (the complement of red), while the same gray on a blue background appears slightly yellowish. This effect extends to hue, saturation, and lightness: colors appear more saturated next to gray, lighter next to dark backgrounds, and shifted toward the complement of adjacent hues. Josef Albers made simultaneous contrast the central topic of his influential 'Interaction of Color' course. Understanding this effect is critical for designers because no color exists in isolation; every color is influenced by its neighbors.