Fuchsine (rosaniline hydrochloride) is a magenta dye. Basic fuchsine is a mixture of rosaniline, pararosaniline, new fuchsine and Magenta II. Carbol fuchsin is a mixture of phenol and basic fuchsin, used in bacterial staining procedures. It is commonly used in the staining of mycobacteria as it has an affinity for the mycolic acids found in their cell membranes. The World Health Organization recommendation of 0.3% carbol fuchsin in the ZN method for staining acid-fast bacilli (AFB).

Tolonium chloride (INN, also known as toluidine blue or TBO) is a phenothiazine that has been used as a hemostatic, a biological stain, and a dye for wool and silk. Tolonium chloride has also been used as a diagnostic aid for oral and gastric neoplasms and in the identification of the parathyroid gland in thyroid surgery. Toluidine blue has high affinity for acidic tissue components, thereby staining tissues rich in DNA and RNA. It has found wide applications both as vital staining in living tissues and as a special stain owing to its metachromatic property. Toluidine blue has been used in vivo to identify dysplasia and carcinoma of the oral cavity.

Evans Blue (EBD) is an azo dye which has a very high affinity for serum albumin. It can be useful in physiology in estimating the proportion of body water contained in blood plasma. Evans Blue Dye is widely used to study blood vessel and cellular membrane permeability as it is non-toxic, it can be administered as an intravital dye and it binds to serum albumin – using this as its transporter molecule. The EBD–albumin conjugate (EBA) can be: (i) identified macroscopically by the striking blue colour within tissue; (ii) observed by red auto-fluorescence in tissue sections examined by fluorescence microscopy; and (iii) assessed and quantified by spectrophotometry for serum samples, or homogenised tissue. has recently been utilised in mdx mice to identify permeable skeletal myofibres that have become damaged as a result of muscular dystrophy. EBD has the potential to be a useful vital stain of myofibre permeability in other models of skeletal muscle injury and membrane-associated fragility. Evans Blue is a potent inhibitor of L-glutamate uptake into synaptic vesicles. It also inhibits AMPA and kainate receptor-mediated currents (IC50 values are 220 and 150 nM respectively). P2X-selective purinoceptor antagonist.

Gentian violet ((GV) hexamethyl pararosaniline, also known as crystal violet, methyl violet) is a triphenylmethane dye with anti-bacterial, anti-fungal, anti-helminithic, anti-trypanosomal, anti-angiogenic and anti-tumor properties. GV has a lengthy history and has been used successfully as monotherapy and an adjunct to treatment in a variety of diseases. Gentian violet interacts with negatively charged components of bacterial cells including the lipopolysaccharide (on the cell wall), the peptidoglycan and DNA. A similar cell penetration and DNA binding process is thought to take place for fungal cells as well. Because Gentian violet is a mutagen and mitotic poison, cell growth is consequently inhibited. A photodynamic action of gentian violet, apparently mediated by a free-radical mechanism, has recently been described in bacteria and in the protozoan T. cruzi. Evidence also suggests that gentian violet dissipates the bacterial (and mitochondrial) membrane potential by inducing permeability. This is followed by respiratory inhibition. This anti-mitochondrial activity might explain gentian violet's efficacy towards both bacteria and yeast with relatively mild effects on mammalian cells.

Acriflavine (ACF) is a topical antiseptic. The hydrochloride form is more irritating than the neutral form. It is derived from acridine. Commercial preparations are often mixtures with proflavine. Acriflavine was developed in 1912 by Paul Ehrlich, a German medical researcher, and was used during the First World War against sleeping sickness. ACF has known trypanocidal, antibacterial, and antiviral activities. Effects of ACF on cancer cells were first reported 50 years ago. By present time was demonstrated that ACF a drug, that binds directly to HIF-1 alpha and HIF-2 alpha and inhibits HIF-1 dimerization and transcriptional activity and thus has potent inhibitory effects on tumor growth and vascularization. Also Acriflavine in combination with 3,6-diaminoacridine (proflavine) could prove to be a potential antimalarial drug and its pharmacological action can be due to inhibition of gyrase activity. This is achieved through interaction of the ACF with the DNA substrate. This interaction may lead to conformation change in DNA unsuitable for binding of gyrase with DNA.

FD&C Red 4 is a synthetic dye produced from petroleum. It is a red coloring pigment, soluble in water. This dye is FDA-approved for use in food, pharmaceuticals, cosmetics and medical devices. Cosmetics applications include: alcoholic perfumes, decorative cosmetics, toilet soap, syndet and liquid tensid products.