The nucleic acids are concentrated in the nucleus and the rough endoplasmic reticulum. The colour is usually some shade of blue or brown depending on the particular method of haematoxylin staining used. Most cells do not have such a concentration of GER that their cytoplasm stains significantly with haematoxylin. Consequently, another cytoplasmic stain is needed. Such a general stain is eosin, acidic in nature, which stains the cytoplasm of most cells red or pink.
Some structures stain bright red.
Three points should be mentioned. The basophilic reaction is a chemical one and different basic stains can be used to show cytoplasm in various colours, red, blue, green, etc. The same principle applies to an acidophil reaction of the cytoplasm. Two stains are used one after the other in the H and E treatment. It is not difficult to get the balance wrong so that one swamps the other.