According to the valuable answer posted from Aliya Ramazanova, please note that the tetrazolium dyes used in the callus research are redox dyes e.g. redox indicators. Please read this link and references cited in it.
Article Use of a New Tetrazolium-Based Assay to Study the Production...
On other part, give in the RG search (at the top of the page) tetrazolium dyes and callus and you will earn a lot of answers /questions about this aspect of callus research. (see p.e. Peter Mazur (RG member) /pdf free of charge/Studies on the reduction of 2,3,,5-triphenyltetrazolium ......
these dyes have another properties than Evans blue or Sudan black B and you must at first read the related papers about them.