On Saturday, January 30, 2016 at 5:45:06 PM UTC-5, Don Johnstone wrote:

I think it is a common finding in this thread that almost nothing
increases the visibility of a glider approaching head on, in fact some
markings may reduce visibility. The frontal area of a modern glider
is so small so with no relative lateral or vertical movement they are
very hard to spot.

The exception to that might be a forward facing narrow beam white LED strobe. Say a 15 degree cone.