Romanowsky stains are commonly used to stain blood films and identify blood components. Some key Romanowsky stains discussed in the document include Leishman, Giemsa, Wright's, Field, Jenner, and JSB stains. These stains involve using dyes like methylene blue and eosin in specific combinations and concentrations to differentially stain structures in blood films based on their chemical properties. Proper staining technique and protocols are outlined to clearly identify red blood cells, white blood cells, parasites, and other components when examining stained blood films under a microscope.