Easiest to match??
Do you know how many different whites there are? None of them are just white, there is a tiny bit of blue, or black, or ochre in them to make it "warm" or "cool". It needs a damn good painter to match an unknown or a faded known formula white.
Anyway, My vote is in for silver, of all the colours (with the possible exception of pooh brown) it is the best at not looking dirty 5 min after a wash.
Downside is that it turns into a "stealth" colour on rainy days.