The onion skin appears with the same color as the previous drawing

I cant make the onion skin appear shaded as it should. it appears exactly as the previous drawing. What could be causing this problem?

in Harmony, press Ctrl+U to open “Preferences” windows,
then click Drawing tab, and choose Onion Skin Render Style to “Enable Shade” option. at last, click OK button.
Done!
http://oi62.tinypic.com/rm6yq8.jpg