Of course I am biased, BUT, IMHO, I would replace the word common with the word POPULAR, and of course as we all know POPULAR i.e. the peoples choice, means a better chance of a higher resale value as more potential buyers will opt for the popular colours.
Having said that, colour choice is personal and resale value did not enter the equation when I chose my Sterling Silver 147. I just liked the overall co-ordinated look, and apparentlly so do a lot of other people.
So, it is what you, the owner,likes that is important, and as long as you have seen the Platinum Grey on the car when you chose the colour, I would not worry if I was in your position.
You will love the car whatever colour it is, whether you are driving it or cleaning and polishing it, with it's subtle curves and seductive lines, and the way the colours give a different impression depending on the light,I am sure you will get years of pleasure from it.