Ever notice in "Snow White and the Seven Dwarfs" -- and nearly every Disney movie -- evil characters wear dark colors, while good ones wear white? That such "contemptible collectibles" as mammy cookie jars are still mass-produced? That "The Big Chill"soundtrack is Motown, but the cast is all white? Patricia Turner, a UC Davis professor, has noticed this and more in her new book, "Ceramic Uncles & Celluloid Mammies: Black Images and Their Influence on Culture." Turner, who studies African-American, African and American culture, shows how mainstream popular culture distorts images of blacks. Because people spend so much time watching television and movies, thinking critically about popular culture is important, Turner says. Images in such media "have an impact on people whether we want to acknowledge it or not. Negative stereotypes are very tenacious. They stay with people." Disney movies, a major influence on children's perceptions, reinforce the message that dark is evil, Turner says. Today, though, children are exposed to a wider and more positive range of messages about different races than in 1937 when Snow White was released originally, Turner says.