Staining with toluidine blue 0 followed by staining with naphthol yellow S results in a striking spectrum of colors which aids in the differentiation of various cell and tissue constituents. New colors, in addition to the colors of the dye solutions, are seen in both metachromatic and nonmetachromatic areas. The nonmetachromatic colors include various shades of blue, yellow, green, and brown or red, and seem to be related to the affinity of the structures to acid and basic dyes. An additional advantage of this staining procedure lies in its ability to enhance and differentiate the metachromatic colors of toluidine blue.SoEutions. The dye solutions consisted of 0.1% toluidine blue 0 (Harleco; C.I. No. 52040) in 0.067 M phosphate-buffered solution of p H 7.3-7.4 and 1% naphthol yellow S (Harleco; C.I. No. 10316) in 1% acetic acid. Biotech Histochem Downloaded from informahealthcare.com by University of Newcastle Upon Tyne on 12/21/14 For personal use only.