Metachromasia

metachromasia [‚med‚ə·krō′mā·zhə]

(chemistry)

The property exhibited by certain pure dyestuffs, chiefly basic dyes, of coloring certain tissue elements in a different color, usually of a shorter wavelength absorption maximum, than most other tissue elements.

The assumption of different colors or shades by different substances when stained by the same dye. Also known as metachromatism.

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Metachromasia 

in biology, the property of cells and tissues that causes them to take on a color that differs from that of a dye. For example, in staining with thiazine dyes, the basic matter of connective tissue, tumor cells, and certain other cells are stained not blue or violet, the color of the dye, but red or pink. It is thought that metachromasia is caused by the polymerization of the dye molecules under the influence of free negative charges in the tissue.