I could be prejudiced, but I'd go with the Mouse. The darker colors seem to emphasize how large this bag is. The lighter color of Mouse softens the bag's line so it's not so "in your face" when you carry it. As much as I love this bag, when I first tried on the black I was taken aback because everytime I looked at myself, all I could see was BAG! I don't feel like that when I'm carrying the Mouse color
If not Mouse, I'd go for the Petrol -- I LOVE that color (in fact, I think I need SOMETHING in that color myself!)
I don't know if anyone has actually seen the "small" Camille IRL but looking at the measurements, there does not appear to be a huge difference from the original Camille. I hope it appears smaller in person.....
I actually talked to my contact at MJ today and he said that there's NOT much of a difference between the Small Camille and the original one. He said it's as if they decided to downsize it slightly, and reduced it by an 1 all the way around. Appearance-wise, he says, it looked the same to him. They haven't arrived in the stores yet, so he hasn't compared it side by side to the original, but he did see it at the Buy and from what he remembers, it didn't look all that much smaller
Petrol Blue is like a dark smokey blue with dark green undertones. From the pics I've seen, it looks a lot like the Petrol from F05
ETA: This is the Petrol Cecelia from the NM website - I would imagine the Camille would be a little bit darker due to the leather