White Legend

I use QwtPlot in my project, and plot have custom gradient background color. But under my *GNU/Linux-based OS* legend have white background. *GNU/Linux-based OS* use Equinox DE (Wiki). Under Fedora 16 legend looks normal.
Screenshot attached. Any ideas?
Attachment 9376

Should be an issue of the style ( see QStyle ) that is derived from the desktop.

Uwe