'rgb - an RGB tuple (three 0.0-1.0 values)
return an allocated gtk.gdk.Color'

def rgb_to_gdk_color(self, rgb):

    try:
        return self._cached[tuple(rgb)]
    except KeyError:
        color = self._cached[tuple(rgb)] = self._cmap.alloc_color(int((rgb[0] * 65535)), int((rgb[1] * 65535)), int((rgb[2] * 65535)))
        return color
