The color of blood in vertebrates is primarily due to hemoglobin, which contains iron that contributes to its red hue. Hemoglobin's derivatives, such as haematin and haematoporphyrin, also play a role in this coloration. In contrast, insects have a different circulatory fluid called hemolymph, which lacks blood vessels and circulates in a cavity within their exoskeleton. The heart of an insect is a long tube that pumps hemolymph slowly throughout its body, taking about eight minutes for a complete circulation.The discussion also touches on the specific factors influencing the color of blood. It is suggested that the red color of hemoglobin is not solely due to iron but is influenced by its molecular structure and the surrounding environment. The color of iron can vary depending on its coordination with other molecules, indicating that both the iron and its molecular context contribute to the overall color of blood in different organisms.