Question

summary of article many colors of blood

Answer 1

Color of Blood is not 'Red' in all animals ,which is most known color of blood to most of us.

We have and image in mind , that blood means Red , we use terms like ' red blood color'.

The requirement for O2 in body is so important , which necessitated special systems for transporting and storing it, which gave origin of color of bloods. . Apart from the difficulty in supplying O₂ to buried tissue, there is the problem of achieving a sufficiently high concentration in aqueous environments.

This problem is overcome by special metalloproteins known as O₂ carriers, which gives color to blood. In mammals and most other animals, these special proteins (myoglobin and haemoglobin) contain an Fe porphyrin
cofactor, which makes our blood red colored . Deoxymyoglobin (Mb) is bluish red and contains Fe(II); this is the oxidation state that
binds O₂ to give the familiar bright red oxymyoglobin (oxyMb .

Animals such as molluscs and arthropods use a Cu protein called haemocyanin : blue colored, Deoxyhaemocyanin (Cu(I)) is colourless but it becomes bright blue when O2 binds. The blue blood of horseshoe crabs contains a chemical that immediately tells whether a drug is contaminated with bacteria.
Some lower invertebrates use an alternative type of Fe protein, haemerythrin, which contains a dinuclear Fe site, this blood appear violet-pink.

Certain bottom-dwelling marine worms have green blood. Sea squirts have purple blood.

Colorless, blood does not contain a respiratory
protein.