how to set foreground/background colour in status bar

Hello,

   I am unable to set colours for the status bar (wxPython under Linux):

my_status_bar.SetBackground( wx.wxRED )
   has not the desired effect. It has _some_ effect, though: when I
move the mouse quickly around on my desktop, and return to the wxFrame,
the red colour appears very shortly, before being overwritten by the
usual black-in-grey.

   I deduce that there is a hidden layer between logical and physical
status bar; I assume I ought to say
   my_status_bar.HiddenSomething.SetBackgroundColour().
If this is correct, I would be happy to know the actual name of
HiddenSomething. Otherwise, I would appreciate any other hint.

    Thanks in advance, Joachim