The 2018 CIVL Section 7:

To improve visibility and make glider identification easier, all
competitor gliders must either display two organiser-provided patches of
contrasting material with competition numbers on their leading edges or a high
contrast graphics or a high contrast nose cone.

Richard Lovelace showed up with a green nose cone that works well
with his new Wills Wing TIII. I've ordered a blue one from Wills. Meanwhile I've
got orange gaffer tape on half of my nose cone. Others have used the tape to
mark their nose cones or leading edges.