Visual Dx -- (available via Website or App access provides) is committed to improving diagnosis in darker skin types. It offers a Skin Pigmentation Filter for search results.
Ebook via Springer
As both experience and evidence-based findings indicate, specific dermatological conditions can prove harder to diagnose in patients with darker skin tones.
Ebook via Springer.
This atlas, containing more than 300 color photos, focuses on those dermatologic conditions that are most common in ethnic skin or skin of color.
Taylor and Kelly's Dermatology for Skin of Color 2/e by 
Clinical Cases in Skin of Color by 
Pediatric Skin of Color by 
Pigmented Ethnic Skin and Imported Dermatoses A Text-Atlas
Atlas of Black Skin
Dermatology Atlas for Skin of Color