Its color is indigo blue to silvery- or grayish blue. Traditionally, jeans were dyed to a blue color using natural indigo dye. G. Biv which stands for red, orange, yellow, green, blue, indigo, violet. Most denim is now dyed using synthetic indigo. Other plantation crops included cotton and indigo dye. Newton's own color circle has yellow directly opposite the boundary between indigo and violet. Helmholtz says "Yellow and indigo blue" are complements. Newton's conception included a seventh color, [[indigo]], between blue and violet. Dye crops of indigo and chay root were produced for the weaving industry. It comes in the colors Indigo and Jet Black. Indigo and cyan are not standard colors. "My Blue Heaven", "Mood Indigo", "One for My Baby (and One More for the Road)". Indole chemistry began to develop with the study of the dye indigo. The five fruit colours were later replaced with Ruby, Sage, Indigo and Snow. However, the correspondence of this definition with colors of actual indigo dyes is disputed.