I got the exact same cable from Derrin a while back. At first, I was pretty angry because I had waited SO long for this cable to arrive (apparently, Derrin was out of M8 connectors) and it was the wrong cable.
On a whim, I decided to hook up two of the three cables, blue and brown. It worked perfectly. I simply left the gray cable disconnected.
Although it took Derrin a long time to deliver the product, the craftsmanship was phenomenal.