[Scribus] Pick background color from image / specify numeric color values

[Kai Großjohann]

I have an image, and I would like to use one of the colors in that
image as the bg color for a text field.  I think I can figure out the
values of that color using Gimp or suchlike.  But how to set the
background color of the text field to that color?

The properties window only allows me to choose amongst some named
colors.  There is also Extras/Color Wheel, but I don't understand what
it does.

Is there a color picker in Scribus?

(I guess I could use the foo color as background color, then use Emacs
to edit the *.sla file and replace the hex values for the foo color in
the list of colors.  But perhaps there is another way.)

tia,
Kai

PS: Newbie with Scribus.  Using the most recent binary install on
    MacOS X.