I think that you may be looking for two documentaries by Riggs which deal
with African-American media images:
 
Color Adjustment (deals primarily with television)
 
and
 
Ethnic Notions, which traces the evolution of deeply rooted stereotypes
(Toms, carefree Sambos, faithful Mammies, grinning Coons, wide-eyed
Pickaninnies, ad nauseam).  Both were distributed by California Newsreel as
of 1993.
 
California Newsreel
149 Ninth Street Suite 420
San Francisco, CA 94103