Why is Tau commander Farsight's (O'Shoh) crisis battlesuit painted red?

Question

In the book Farsight by Phill Kelly, Farsight's answer in response to Brightsword's question regarding why he had painted his Crisis battlesuit deep red was:

You asked me why I changed my battlesuit colours. It is to honour the Arkunashan dead. Their blood is on my hands, and I will not forget it.

This is a compelling reason for a human who is seeking to avenge his fallen comrades. But the thing is, Arkunasha is a Tau Empire colony and Tau blood is blue or cyan^[1]. Shouldn't he have painted his suit blue instead?

Why did Farsight choose a red paint scheme to honour the Arkunashan dead? Do any of the Warhammer 40k supplements or general lore explain this discrepancy, or is this just an honest mistake? Note that GW depicts Commander Farsight in a red Crisis Suit.

---

After ShadowKras' answer, there is no doubt regarding Tau blood: it is definitively blue (or cyan to be more precise). This leaves us with the original question: why is Farsight's suit red?

As for now, I can only think of one possibility myself. Given that Farsight is a WH40K character that has been there long before the book Farsight, Phill Kelly tried to justify the suit's color by relating the to spilled blood, but made a honest mistake by not remembering that Tau blood is blue.

Can anyone confirm/deny this? Is there a different reason why the suit is red?

Answer 1

Legacy from the previous codex editions

We known that, currently, Tau blood color is officially cyan, as seen on the Xenology book, published by Games Workshop. There, we have a dissected (female) Tau and an audiolog describing their physiology that says that the specimen's blood is a blue fluid, and that its skin is grey/blue.

While there are many debates online about the color of Tau blood, this writer goes great lengths to explain why he believes that blue is correct and describes the biological consequences:

To have cyan blood, the tau would need to have a circulatory system comprising of a plasma with free floating oxygen carrying Hemocyanin, which unlike human blood is not infused in corpuscles cells (hemocytes, blood cells), due to it’s size (larger) and nature (relation to oxygen and carrying it). To be as efficient as hemoglobin, most hemocyanin users have high density of blood.

For tau, it would account for their strong grey-blue complexion. Therefore, the less oxygen a tau has, they more grey faced they become, then white and die.

Tau, by this (I believe far better fitting) theory, have a blue blood circulatory system based on Hemocyanin usage.

But Tau blood has been depicted as red by artists like in this artwork (I meant this artwork), and sometimes they have red blood on Warhammer games, too, like in this screenshot.

This confusion may have been caused by the previous editions of the Tau Codex (ver. 3) mentioning that their blood was red during the Ta'lissera (the bonding ritual). This reference has disappeared from the newest codex.

The blood of his brothers-to-be would soon coat its blade with a ruddy red sheen and the enormity of what they were about to do both thrilled and scared him.

Both the Firewarrior and For the Emperor novels claims that Tau blood is cyan. Since those books are newer than the Codex, this is considered official canon.

Also, the official Web site has the color palette for Commander Farsight if that's useful.