Peridot is one of the few gemstones that occur in only one color, an olive-green. The intensity and tint of the green, however, depends on how the percentage of iron that is contained in the crystal structure, so the color of individual peridot gems can vary from yellow to olive to brownish-green. In rare cases peridot may occur in a medum-dark toned, visually pure green with no secondary yellow hue or brown mask.

Credit : https://en.wikipedia.org/wiki/Peridot