text: No. Not all animals bleed red.\n\nWarm-blooded animals have red blood because they have the pigment hemoglobin.   Hemoglobin is the pigment in warm-blooded animals that carries oxygen molecules from the lungs throughout the body.\nHemoglobin is red, related to the iron atom at the center of the molecule.  \n\nInsect blood, for example, does not have hemoglobin, and is clear ... although it can appear green or yellow, most likely from chlorophyll from the plants it eats.  (Chlorophyll is the pigment in plants used for photosynthesis.)\n\nInterestingly, the chlorophyll molecule in plants is very similar to the hemoglobin.   The main difference is that chlorophyll has a magnesium atom in the center, rather than iron, and this is what makes chlorophyll green, while hemoglobin is red.