Hi Kev, I am sure others will correct me, but the guide does have to be black. I have painted these in the past, but the wear and tear on the guide soon makes it rub off - usually half way through the race when you are blocked by a slow pace car! As to distance for the sensor, the furthest back I have a sensor from the slot gide is just over 1 1/8" and it works perfectly. Scalextric Aston Martin DB5, Cooper T53 and Mclaren M23, to name a few. However, I run the old Scalextric C7042 6 car powerbase and RCS64 RMS - I do NOT use any of the Arc sets and have no idea whether this makes any difference. From this forum, most advice seems to be to get the sensor as close as possible! Cheers Chas