I guess this is a bit of a test of the quality of the monitor's colour display. The differences are clearer in real life than they are on this computer. I've put a scrap of the undyed yarn on top of the dyed skeins: beige on the right, grey on the left. These are both natural fleece colours and the grey in particular look quite distinct to me, but they over-dye remarkably well. There's just a slightly different shading in the colour between the two. Now to admit, they're not quite dry yet, so I'll need to wait a little before I can wind them off and put them to use.