In DEI parlance, black and brown refers to African-Americans and Latinos, although, curiously they also do accept African H1B visa holders in this group, despite them typically having high education, wealth from home, etc.
When I have read writings on DEI, they usually talk about "African-Americans," a term historically used to refer to the descendants of slavery. Which writings by DEI professionals and experts have you read that say African H1B visa holders should be included in DEI initiatives?