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This is the reference and the abstract.
J Cutan Pathol 1991 Dec;18(6):436-9 
Immunoperoxidase technique modified by counterstain with azure B as a
diagnostic aid in evaluating heavily pigmented melanocytic neoplasms.
Kamino H, Tam ST
Department of Dermatology, New York University Medical Center. 
Heavily-pigmented melanocytic neoplasms are difficult to evaluate on
routine hematoxylin and eosin stained slides because pigmented
melanocytes are difficult to distinguish from the numerous melanophages
that are usually seen in the background of these lesions.
Immunoperoxidase staining for S100 protein or HMB-45 antibody using
diaminobenzidine (DAB) as chromogen, which forms a brown product, does
not adequately distinguish melanocytes from melanophages. We modified
this technique by replacing hematoxylin as the counterstain with azure
B, which stains melanin green-blue. Thus, positive melanocytes appear
brown while melanin granules in their cytoplasm are green-blue. However,
negative melanophages only stain green-blue. This technique is useful in
evaluating heavily pigmented melanocytic lesions such as malignant
melanomas, melanosis of regressing malignant melanoma, residual
malignant melanoma in areas of granulation tissue with melanophages,
blue nevi, pigmented spindle cell variant of Spitz's nevi and combined
nevi. 
PMID: 1723081, UI: 92129698 

William B. Tyler MD
Department of Pathology
Geisinger Medical Center
Danville, PA