I *suspect* the colour choices are do to with some sort of value judgement around PCP GFV's or Das Welt resale values.
What you don't want is to be giving different values for colours I suspect, so you pick a load of safe colours.
Although having said that, the "purple nasty" seems to break my conceptual rule ;-)
I swear that was offered as the one zero extra cost option to make people spend more money!!!
Possibly reflex silver was seen as a bit old hat - from ~2000 everyone wanted a pure silver car before that evolved into more grey silver before going back to white as the fave. Certainly the sales figures seem to reflect that broad public group think.
I'd love to talk to VW UK about what their thoughts are on this subject.