Sepia is a black-brown color with a reddish tone. It is named after the sepia cuttlefish and other marine creatures from which this pigment derives. Sepia is a warm neutral color and the two colors that produce it are brown madder and olive green.
In photography, the sepia effect is a tonal editing technique that adds a warmer tone that gives an image a vintage or antique, timeless and archival quality. The sepia effect works exceptionally well with black and white images.
In essence, sepia is a form of photographic print toning. It is a tone added to a black and white photograph in the darkroom to add warmth to the tones in the photograph. However, because the image is still a monochromatic image, it is still considered black and white.