The UK ATC VGS gliders had orange flourecent stripes put on the wings as a result ( I believe, could be wrong on this) of a gliding accident at Sealand back in 95.
Massively increases vis, especially, as you say, of gliders habit of flying round the bases of clouds. As a former glider pilot, always scares me witless when you get radar descended through the significant cloudbase on a bubbly day; you could argue the transoport aircraft is likely to win; not an experience I would wish to experience though. (I belive all composite gliders are particularly difficult to see on Radar).