Many are used as dyes (see azo dye). Each band can be detected using stains such as Coomassie blue dye or silver stain. Color used as a dye can be diluted. Aniline Yellow is a yellow azo dye and an aromatic amine. The first azo dye was aniline yellow. Aniline Yellow was the first azo dye. It is a synthetic lemon yellow azo dye. The color of denim is due to indigo, the original vat dye. They are found in cosmetics, inks, and liquid dye lasers. This is the actual color of the dye. Normally, the henna will dye skin orange for up to 2 weeks. This compound is a common hair dye. They may also dye their hair brown and get artificial suntans. Cuttlefish ink was formerly an important dye, called sepia. It does not dye as well as cotton.