Lots of people seem to like Trophey Blue. Personally I quite like X-Power grey.
It's personal choice at the end of the day.
Have you had a look at the 'Your Motors' section of the main site - may give you some idea, quite a few colours on show there.
Something to be aware of on re-sale... yes a long way off I know.
But having just traded my F (Tahiti Blue) in for a TF (Trophy Blue), I was told that it was lucky my F was not in BRG as people are not interesting in buying that colour as it is too common. So don't jsut go for the colour you think everyone will like as it may be too popular. In otherwords buy the colour YOU like and ignore the resale.