It's red because of the red blood cells (hemoglobin). Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn't change from red to blue. It changes from red to dark red.
There's no need to build up the suspense: Blood is red. It might vary from a bright cherry red to a dark brick red, but it's always red.
Blood is always red. Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red. Anyone who has donated blood or had their blood drawn by a nurse can attest that deoxygenated blood is dark red and not blue.
Sometimes blood can look blue through our skin. Maybe you've heard that blood is blue in our veins because when headed back to the lungs, it lacks oxygen. But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion.
When you cut a vein, the blood is exposed to all of the oxygen in the air, and the hemoglobin in the red blood cells binds to that oxygen just like it would in your lungs, turning the blood bright red.
Specifically, there is an oxygen-carrying protein in each red blood cell, called hemoglobin. This protein has iron molecules that bind to oxygen, giving it a bright, rich color. However, when blood is exposed to air, the oxidation gives it a brownish hue. You can think of brown blood as simply being “older” blood.
Freshly dried bloodstains are a glossy reddish-brown in color. Under the influence of sunlight, the weather or removal attempts, the color eventually disappears and the stain turns grey. The surface on which it is found may also influence the stain's color.
This leaves only high-energy blue light to be reflected from our maroon veins. So, if you cut yourself in space, your blood would be a dark-red, maroon color.
In many anatomy books, some veins are colored blue. These observations may have led you to question the actual color of blood. So… is blood ever blue? Well, the quick answer is no, human blood is always red.
Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn't change from red to blue. It changes from red to dark red. It is true that veins, which are sometimes visible through the skin, may look bluish.
The red light is absorbed into the hemoglobin within your blood, turning internal blood red. Since blue wavelengths do not travel as far, the color is not absorbed in the same way. The result is the appearance of blue or green veins from the surface.
Deoxygenated blood is darker due to the difference in shape of the red blood cell when oxygen binds to haemoglobin in the blood cell (oxygenated) versus does not bind to it (deoxygenated).
Veins appear blue because blue light is reflected back to our eyes. This may seem odd, since veins contain deep, dark red blood. Scientists believe there are several factors that lead to our seeing veins as blue rather than red. Blue light does not penetrate human tissue as deeply as red light does.
It is always red. Even when it's deoxygenated. Even in the absence of oxygen in a vacuum.
In general, normal blood temperature is about the same as normal body temperature, or about 98.6℉ (37℃). Blood outside of the body will remain the same temperature for only a few minutes. After a few hours, blood cells will die and the blood will reach room temperature.
Hemocyanin pigment contains high copper levels in it. Due to the copper content in this pigment, blood appears blue in color. Examples of animals having blue blood are crustaceans, squid, and octopuses. Crustaceans, squid, and octopuses have a blood color of blue.
A blue blood is an aristocrat. Blue bloods come from privileged, noble families that are wealthy and powerful. The word blood has long referred to family ties: people you are related to share the same blood.
Great question, Sita! The short answer is ants have something similar to blood, but scientists call it “haemolymph”. It is yellowish or greenish.
Thus, in the cockroach, the hemolymph is colorless. The blood of the cockroach does not carry oxygen and also they don't have vessels. So the blood of cockroaches can be said to be colorless or white as well.
Raman spectroscopy and advanced statistics allow the researchers to date a blood stain accurately, provided said blood stain is less than two years old. Raman spectroscopy involves shining a laser on a sample and measuring the intensity of scattered light.
As blood leaves the heart and is oxygen-rich, it is bright red. When the blood returns to the heart, it has less oxygen. It is still red but will be darker. This darker red appears blue because of how light travels through the skin.
As fresh blood is red in color due to the present high level of oxyhemoglobin and after sometimes when oxyhemoglobin oxidizes into methemoglobin blood changes to dark red to bluish color and finally oxyhemoglobin changes to hemichrome results in dark brown color.