Gram Color is a staining set for staining microorganisms by the Gram method. • Aniline dyes in the cell tissue of microorganisms from a red dye-iodine complex when exposed to iodine. • In gram-positive microorganisms the dye- iodine complex cannot subsequently be dissolved from the cells with decolourizing agents such as alcohol or acetone. • The cell remains blue-violet. • In gram - negative microorganisms the dye - iodine complex is dissolved and the cell turns pink to red as a result of counterstaining.