There is no comment about ferrite. The solution is 100ml stock solution and 1g potassium metabisulfite, K2S2O5. The stock solution is 24 g ammonium difluoride, 1000ml water, 200ml conc. Most samples were partially transformed only, so the remaining austenite formed martensite upon water quenching. Ferrite is white or lightly tinted.
Pearlite is multicolored.
Bainite can be seen in color also. Examples of these structures are given for all three etches. Klemm's I can also be used. It colors ferrite strongly, but also colors other constituents. Nital darkens martensite, but not ferrite.