Blood

Biological Use

Blood is used to transport nutrients through the body of a multicellular organism. In the case of humans, it uses a compound called hemoglobin to transport oxygen to the cells. Because of cellular respiration, every single cell in the human body needs oxygen, so blood must deliver oxygen to every cell in the body. This is most likely true all of the other Covenant races, though their blood may be delivering a different compound to the body, resulting in its difference in color to human blood.

In the Halo Series

When shot without the protection of an energy shield, the target will "bleed." In some races, the blood will visibly come out of the target, and leave a stain on the ground. The viscosity and color of the blood varies by race.

Covenant Species

Sangheili - Dark Blue (Halo: CE)^[1], Purple (Halo 2 and Halo 3).
Jiralhanae - Black (Halo 2), Red (Halo 3).
Mgalekgolo - Orange.
Kig-yar - Purple, thick^[2].
Unggoy - Light Blue, teal^[3].
Yanme'e - White.

Others

As in reality, Humans will bleed red blood when shot. The Flood will always bleed a pastey, brownish-green color, and the explosion of a Carrier Form or an Infection Form will leave a brown stain on the ground. Regardless of the host organism, Flood combatants will always bleed a brown colored blood.

Sources

^ Bloody.jpg (Corpse was meleed multiple times.)
^ Halo: The Fall of Reach, page 126
^ This image

Trivia

- In Halo: CE, Elites and Jackel blood appear the same color when they are punched multiple times

- In Halo: CE, Elites and Jackels bleed the most when punched.

- In Halo 3, there is no blood when playing splitscreen

[1] Bloody.jpg (Corpse was meleed multiple times.)

[2] Halo: The Fall of Reach, page 126

[3] This image

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