The red wunz go fasta comes from way back when they painted their war-animales with blood laced with drugs as far as i understood it . .
And because the animals that were painted like this DID in fact, go fasta, other orks who did not know about the drugs thought it was the colour alone.
and this belief shared by enough orks has, through the power of the WAAAAGH!, actually made that belief come through.
And it has carried on and over untill they had their first vehicles and dakka too.
Of course, i am probably horribly wrong.
