inkscape -z -i blue -j -l blue.svg drawing.sv
This extracts the object, all right, but it doesn't appear in the right place, so that the icon is blank. For example, drawing.svg has a blue rectange (ID blue) whose dimensions are shown in the UI as height 150, width 200, x=100, y=625. The height of the document is 1052.36220 (A4 at 90 dpi.) When I look at drawing.svg in a text editor, there's a little rounding: