... but the comments from Kari let me have a very small doubt.
You can try your luck but I assume you should prepare your arguments well if you write a letter to Geneva.
But in case they agree (which I still doubt), be prepared to not only pay a bunch of money but also forget your original dial (for this I am certain, they will NEVER give it back to you). So you'd better be sure before you ask so as not to regret your choice !
Both grey and black dials are nice on the 5205G but they really look different to such an extent that almost the watch itself looks different (I exagerate only a little). I mean they look so different that I believe they address a different clientele. And if you choose the dark dial originally, you might not feel happy in the long term with a silver one.
Ideally, find a friend who owns a 5205 with silver dial in your city and try to convince him to do a temporary swap for 1 or 2 weeks and then decide...
Good luck and let us know the outcome.
Best,
Mike