I actually had the good fortune of going to an AD today and finding the 42 in grey and blue and the 38 in silver.
Just my two cents, but I found the 38 to be a bit insubstantial, both literally and figuratively. It just didn't feel very special to me....and it didn't feel like a 10k watch....
The 42, on the other hand, has an amazing mix of masculinity, modernity, class and style with a subtle touch of the 70s feel.
It just felt special, and worth the price of admission.
Now the question remains, blue vs grey??
That's a hard one, with my head saying blue and my heart clearly saying grey.
The blue is a beautiful blue, no doubt, but it is a bit more sport while the grey is a bit more chic. I suppose it depends for what one wants the watch, and what is the rest of the collection.
I also found the grey, which a touch of brown undertones, to complete the overall aesthetic in a slightly more harmonious way, while the blue demands attention on its own.
Maybe if I go back wearing a blue suit instead of a grey suit I'll feel differently? LOL. Who knows. Most importantly, I think the 42 is a fantastic watch no matter the color.