While I don't do much training at night, riding at night is a necessary part of a 100 (at least at the speeds I do 100s!).
I like to be able to see the trail--after a horrible experience of being out on trail with no lights and a bunch of glowsticks that failed as trail markers, I don't go out without illumination. Dream sports lights on her breastcollar and I use a headlamp on the red setting. The white lights being below and behind her head (and shining down at the ground) don't mess with her night vision and the red light is enough to warn me of branches to duck, etc.