I can understand that 'our' gliders present a few challenges to other pilots transiting know gliding operational sites and elsewhere.
Radio calls when doing so are indeed welcome, but if there are (say) five gliders in the air at that location, we're unlikely to be of much assistance if each of the airborne aircraft replies with their altitude, position and intentions, because it's quite likely that all of them will have a different story to tell (Multiply by the additional aircraft number where applicable). I agree that it's bad if there is a wall of silence. Ideally the instructor for the day should be the one to respond - or secondarily the duty pilot or log keeper. Even then, all that can be realistically offered is a broad report on how many gliders are airborne, and (perhaps) an indication on how high convection is going. No-one is likely to be above that level.
Similarly, when out of a task somewhere (or indeed at any time for that matter) our altitude is unlikely to be a constant factor - we'll be descending when on glide, and most likely circling when climbing. I still agree that spot altitude, speed, heading and intention should willing shared when asked, but when the primary details are under constant change, everyone will soon tire of five or ten minute transmissions from every glider on the frequency in use (which is another variable anyway).
All modern "GRP" gliders are white - they have to be for structural reasons - few places more critically so than in the harsh Australian summer sun. We've tried conspicuity (Dayglo) markings on non critical surface areas, but it proved to be not worth the complication - there was no benefit. Ditto for for strobe (or led) lights in the obvious locations. Again, it didn't noticeably improve the visibility of the aircraft so equipped. Conversely perhaps, the visibility from inside most gliders is about as good as it gets.. For the most part, we have a pretty well unobstructed view of the air into which we are flying which leads me to a further point.
I can assure you that all glider pilots have "constant lookout" drilled into them right from the very beginning of the instructional flights. Whether they continue to do so into their solo flying adventures can't be monitored effectively other than by the individual themselves - or PNF if there are two POB. The check instructor on the annual flight check flight(s) is invariably watching for this, and will be quite scathing if it's deficient. I know from my own flying that one tries to keep a constantly updated mental picture of where the others are. Every time there is a collision of any sort between any aircraft, anywhere, we take the event and the consequences on board, and apply any lessons learned to our own discipline the next time each of us is enjoying the privileges and all the other emotions and experiences that being able to fly bestows on us. That is about the only good thing we can take out of the two sad collision events which have been under discussion here and elsewhere in recent days.
Please note that I no longer fly - my comments are based on how it was when I was closely involved. I do keep up with subsequent developments, and for the most part, I think my comments would be valid in the current situation - at least where I used to fly.