The reddening of the white matter is also frequently likened to staining with blood (see dye). Theophrastus compared the reddening of the slain, white Mercurius in its own blood to the dyeing of a white garment in *Tyrian purple
Abraham identifies dyeing—specifically the Tyrian purple staining of white cloth in blood—as the canonical alchemical image for the rubedo’s transformation of the whitened matter.
, A Dictionary of Alchemical Imagery, 1998thesis