Look for stereotypes. Look for tokenism. Check to be sure that the illustrator has not simply used white characters colored in and that all people of color do not look alike. Examine who is doing what.
Some words carry insulting or derogatory connotations.
The copyright date is no guarantee that a book is nonbiased, but more recent books generally present a more authentic view of people of color and women than those published in the 1960 s and before. The information was adopted and reprinted from the Council on Interracial Books for Children, Inc.'s publication.