Are "white" and "black" ever capitalized when referring to people?

According to CMS, when referring to racial categories, use whites or white people, blacks or black people, both of which are written in lower case.

Chicago Manual of Style, 16th edition, 8.39, p. 402.

However, according to APA, racial and ethnic groups are designated by proper nouns and are capitalized: Black and White.

APA Publication Manual, 6th edition, 3.14, p. 75.

Therefore, follow the style guide used in whatever discipline or genre you are writing.

Racial and ethnic groups are designated by proper nouns and are capitalized. Therefore, use Black and White instead of black and white (the use of colors to refer to other human beings is currently considered pejorative and should not be used). Unparallel designations (e.g., African Americans and Whites; Asian Americans and Black Americans) should be avoided because one group is described by color while the other group is described by cultural heritage (American Psychological Association 2012).

APA. (2012) Publication Manual of the American Psychological Association.

(Sixth edition). (p. 75) Washington, DC: American Psychological Association

Some news sources say they will capitalize "black", but not "white". Others capitalize both.

AP says it will capitalize Black but not white

Columbia Journalism Review, the Wall Street Journal, The New York Times, USA Today, the Los Angeles Times, NBC News and Chicago Tribune are among the organizations that have recently said they would capitalize Black but have not done so for white.

“White doesn’t represent a shared culture and history in the way Black does,” The New York Times said on July 5 in explaining its decision.

CNN, Fox News and The San Diego Union-Tribune said they will give white the uppercase, noting it was consistent with Black, Asian, Latino and other ethnic groups. Fox cited NABJ’s advice.

CBS News said it would capitalize white, although not when referring to white supremacists, white nationalists or white privilege.

I personally think that the justification by the New York Times is absurd. If "white people" aren't a group, why are you even referring to it?

It is a style issue. The NYT started doing it and then it was a thing. However, capitalizing Black and White and Brown is poor grammar. Simply, we only capitalize proper nouns in English.

black, white, brown

African-American, Caucasian, Asian (among others)

"African American" is going out of style possibly because so many black people are not African. Haitians in particular are modestly offended by the term.

Style is one thing, but bad grammar is against my good sense. I'm keeping it black, white, brown - at least until Chicago makes the change. The 17th Edition did not make a change, and the 18th is probably still a few years away.