What a difference a color change makes

These are three incarnations of the same painting.  The first picture was taken after about thirty minutes of work from a live model.  I think it looks fresh and complete, and I might very well have stopped there.  The second  is the same painting after three hours of work.  It may be more refined but it is not particularly better, in my opinion.  I used the orangish tan back ground because it was close in color and tone to the original canvas color, which I thought was working pretty well. In the third example, I have decided that the warm background wasn't working, so I changed it to green.  I don't know if this is better or not. It is different and it contrasts with the skin tones, but that neutral background seems kind of pointless to me.  It might be better if I made it very dark - black, even.  Or put some objects in it. Or just moved on to another painting.  This is all practice, after all.