Illuminating Traffic Cones at Night Using Battery Powered Lights Inside Them - Runner Night Vision

One of the challenges to conducting nighttime trail run events is providing lighting on the course that doesn't mess with the runner's night vision. Each runner has their own head or body mounted LED lights to illuminate the trail, but when we have these check points to manually track their bib numbers (for safety reasons, not timing), we need to make it obvious they need to check in with us. We want to do that without totally screwing with their night vision that their eyes have gotten used to, because the trail beyond us will be very, very dark, lit only by the moon.