My view is to forget the "exclusivity" factor.
Who knows if colours will be made available on other models in the future, unless it is advertised as a "signature colour".
My advice is to simply choose the colour you like best. I am really pleased with my Atlantic Blue GTD. In the sun, the flakes shimmer and the car looks stunning.
In my view (and it's only a personal choice...!) there are so many white, silver and grey Golfs around, the blue is something different. My last GTD was Limestone, which was nice, but a bit dull. It certainly never shimmered the way the Blue one does now.
But ... we all have different opinions ....!