"YELLOW BLACK AND BLUES" -Crystalline citric acid found in citrus fruit"Yellow Black, and Blues" is a photograph of citric acid crystals. Citric acid is found naturally in citrus fruits and is an antioxidant. This photograph was taken through a microscope, a technique known as photomicrography. The crystal facets create the colors naturally by refracting transmitted white light, separating it into the colors of the spectrum.