Lou Jing sings Shanghai opera and speaks fluent Mandarin, but when she competed to be China's next reality TV pop star, it was not her voice that was criticised -- it was her black skin.

The daughter of a Chinese mother and an absent African-American father, 20-year-old Lou caused a media storm when she was named one of Shanghai's five finalists for "Let's Go! Oriental Angel," an "American Idol"-style show.

Lou Jing ... I felt hurt. I never meant to offend anyone.

But her fame has been for all of the wrong reasons, after her appearance sparked a vigorous and often vicious nationwide debate on whether she was even fit to be on Chinese television because of the colour of her skin.

Ahead of US President Barack Obama's first visit to China, Lou's experience has put a spotlight on perceptions of race in the country and the challenges the Asian giant faces as its economic boom fosters a more ethnically diverse society.