 ), which are metachromatic due to switching from monomeric to stacked aggregates, Alcian blue is apparently orthochromatic.In common with Astra blue and other similar dyes, this property that it does not change color either by change in concentration or by combination with substrates, makes it very suitable for microspectrophotometry.The apparent lack of metachromasia is not because it is truly orthochromatic but because "it is already fully metachromatic" in aqueous solution.