The colour blood red is a dark
shade of the colour red meant to resemble the colour of human
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells.
Blood is com ...
(which is composed of oxygenated red
erythrocyte
Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood ce ...
s, white
leukocytes, and yellow
blood plasma
Blood plasma is a light Amber (color), amber-colored liquid component of blood in which blood cells are absent, but which contains Blood protein, proteins and other constituents of whole blood in Suspension (chemistry), suspension. It makes up ...
).
It is the iron in
hemoglobin
Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...
specifically that gives blood its red colour. The actual colour ranges from crimson to a dark brown-blood depending on how oxygenated the blood is, and may have a slightly orange hue.
Deoxygenated blood, which circulates closer to the body's surface and which is therefore generally more likely to be seen than oxygenated blood, issues from bodily veins in a dark red state, but quickly oxygenates upon exposure to air, turning a brighter shade of red. This happens more quickly with smaller volumes of blood such as a pinprick and less quickly from cuts or punctures that cause greater blood flows such as a puncture in the
basilic vein
The basilic vein is a large superficial vein of the upper limb that helps drain parts of the hand and forearm. It originates on the medial ( ulnar) side of the dorsal venous network of the hand and travels up the base of the forearm, where its ...
: all blood collected during a
phlebotomy procedure is deoxygenated blood, and it does not usually have a chance to become oxygenated upon leaving the body. Deoxygenated blood is sometimes misconstrued as being
blue
Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical spe ...
.
Arterial blood, which is already oxygenated, is also already a brighter shade of red— this is the blood seen from a pulsating neck, arm, or leg wound, and it does not change colour upon exposure to air.
The colour "blood red", therefore, covers both these states: the darker deoxygenated colour and the brighter oxygenated one. Also, dried blood often has a darker, rust-coloured quality: all dried blood has been oxygenated and then desiccated, causing the cells within it to die. This blood is often darker than either shade of red that can be seen in fresh blood.
In the RGB colour spectrum blood red often consists only of the colour red, with no green or blue component; in the CYMK colour model blood red has no cyan, and consists only of magenta and yellow with a small amount of black. It is frequently darker than either maroon or dark red.
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Variants
Different sources have proposed different color schemes for the color blood red. Below are some of these.
See also
* Oxblood
* Theatrical blood, which can come in a variety of colours (including shades not found in real blood)
References
{{shades of red
Blood
Shades of red
Color