If you look through the various related threads (there are some in Private Flying as well) you will find there are good reasons why the white Tutors and all those white gliders have to be white - it's to protect the airframe from heating. At present this is no neat solution I know of to this, hence Tutors etc. and modern gliders are white and will stay white.
Therefore, ways of avoiding collisions with hard-to-see aircraft have to be sought given that there are a lot of them around and will be for a long time to come.