Some birthstone colors are red for pyrope garnet, blue for aquamarine, purple for amethyst and green for peridot. Other colors include orange for topaz, iridescent for pearl and multicolor or black for opal.
Most gemstones come in a very wide range of colors. For example, garnet, the January birthstone, has orange and green varieties in addition to the more widely recognized red version. Similarly, most diamonds are white, but rare colored versions of the gemstone can come in shades of red, yellow, blue, green or brown.
Other stones tend to come in varying shades of the same color. The emerald, for example, comes in shades of green. The darker the green hue of the stone, the more valuable it is. Amethyst is the February birthstone and comes in shades of purple that range from pale lilac to deep violet.
Other stones have somewhat irregular coloring. Pearl, the June birthstone, changes color based on the light. Depending on the variety, pearls can be white, brown, blue, black or silver, and all have an iridescent sheen. Opal, the October birthstone, displays a rainbow of colors, including reds, blues, yellows and greens. Like the pearl, an opal's color changes as the light shifts. Rarely, opals are all black, and this variety is highly prized.