Was actually yesterday morning, but it was the guy with white lights on the front and rear of his bike.
I was heading up Craigleith Hill Avenue around 06:15 yesterday and saw, through the pre-sunrise gloom, two bikes away ahead - one heading downhill, one uphill. I started to get a little confused as the one coming towards me didn't get any closer, so I thought that perhaps it had stopped. Then it dawned on me that it was maintaining a similar gap even though I was (or believed I was) approaching it.
Only when I caught up with the two bikes on the Craigleith path did I see that the guy had front lights fitted to both the back and front of his bike. The lady he was with had, sensibly, a red rear light.
I sometimes wonder if he's ever had his eyes open at any point in his life and noticed that every other vehicle and bike has red lights at the back. Mind you, it's not as dangerously confusing as the guy with a red light on the front of his bike last winter. I thought I was coming up behind someone, only to realise just in time that he was heading for me...