Test Details: Sudan Black B has been used to stain phospholipids and intracellular lipids. Sudan Black B can be used to stain older blood or bone marrow smears, but the stain slightly fades over time. Sudan Black B stains phospholipids grey and neutral fats blue-black. This test is useful for the differentiation of Acute myeloid leukaemia (AML) from Acute lymphoid leukaemia (ALL).