The microscopic structures of five iron-carbon alloys (including hot rolled 37Mn5, mediumtemperature tempered 65Mn, as-cast QT400-18L, hot rolled P92 and annealed 20 steel) and one titanium alloy (quenched after hot forging) were investigated by using the color metallographic technology and "black and white contrast" metallography. It was shown that the "black and white contrast" metallography could only be used to observe the microstructure of conventional carbon steel and low alloy steel. Three color metallographic methods which were easily operated can be used to observe the ferrite grains in QT400-18L. Heat dyeing can be used to observe the metallurgical structures of carbon steel and low alloy steel in industrial mass production.