Colour problem when capturing a png of the top panel of the screen

I want to capture a window as a png from within a bash script, using the window's *ID*. In this case, the window is the top panel.  Using gnome-screenshot the colours are true, as per this image... (this image is not the same size as the following image, so ignore the dark line at the bottom) However when I capture the panel via import, *or* xwd + convert, I get the following image.. Why would I be getting this colour aberration? import and convert both belong to the imagemagick package... I haven't found anything else in the Ubuntu repository which can capture a window by its *ID*... so I'm stuck. (gnome-screenshot doesn't have the feature)... It would be nice to know what is going on here (eg, is is something to do with *transparent* images, which I know very little about)...but in any case, just a recommendation of a *workaround* capture utility may do the trick ... it must be able to capture a window by it's *ID*.    Here is an example of how I make and view the image capture. import -window "$(wmctrl -l |grep "Top Expanded Edge Panel" |awk '{print $1}')" screen.png display screen.png