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Tan
Quartz is often the main component of sand, because it is very hard and takes a long time to be broken down by weathering. Quartz comes in several different colors, from clear, to white, to brown and even pink. When sand grains with these colors mix together, they appear light tan when viewed from a distance. Other substances like apatite and broken-down bits of coral and seashells may also impart a tan or beige color to sand.
White
Both limestone and clear quartz particles can result in brilliant white sand. The characteristics of limestone sand are quite different from quartz sand, however. Unlike the hard and durable quartz grains, limestone is relatively soft and weathers easily due to water, wind and mechanical abrasion. As limestone sand wears down, it breaks into smaller, dusty particles. It also packs together more firmly than quartz sand and is frequently used to construct roads and paths for this reason.
Black
Black sand is usually derived from volcanic sources. Basalt sand is essentially crushed-up lava rock, and appears opaque and dark gray or black under a magnifying glass. Pyroclastic sand -- sand formed from the pulverized stone of cooled lava flows -- is similar, but it may be glassy-looking and have small holes through individual grains. Some pyroclastic sand is also described as resembling cinders. Magnetite sand is also black, and can be identified easily because it is magnetic.
Other Colors
Though less common than tan, white or black sand, some beaches appear pink because of a high concentration of material from coral reefs. Tiny mineralized plankton remains and crushed shells may also lend sand a pink hue. Sand can also appear green when there is olivine, chlorite or apatite present in large quantities. Apatite also appears in yellow or amber-colored forms. Chlorite is rare, usually found only near the exposed calderas of ancient volcanoes.