Learn how to use this product Erythrosin B stain for use with the LUNA™ family of automated brightfield cell counters. The Erythrosin B Stain is a non-toxic, safe dye for the assessment of cell viability. Erythrosin B can not penetrate intact cell membranes of viable cells, meaning that only non-viable cells are stained red and the viable cells remain colorless. Erythrosin B is compatible for use with the LUNA-II™, LUNA-FL™, and LUNA-FX7™ cell counters.