Good Point Gary, the speaker cable I had was marked all the way along one of the pair of strands to identify it - with a thin coloured line. When I upgraded the cable (the cheap cable was translucent pink) the new set had a raised ridge on one of the strands.
Don't be tempted to salvage some very thin speaker wire off a cheap old midi system as my friend wanted to - his excuse was that he could 'hide' the thin cable easily.
When I bought my Speakers I was surprised that in the instructions I was told not to wire them into the mains ???