Pastel tints of green, purple, and blue in some Deep Sea Drilling Project cores commonly alter to white and yellowish gray after exposure. Most of the color changes take place in young, calcareous ooze that had accumulated at moderately high rates. Very commonly a color boundary is the only striking feature in cored intervals of sediment of nearly identical composition and texture. These boundaries apparently mark the progression of subtle diagenetic changes in the sediment. Color has been used for defining stratigraphic units in deep-sea sediments. The ephemeral nature of color, however, makes it a poor basis for defining stratigraphic units within late Cenozoic calcareous ooze.