They are each beautiful options for the cabas chyc. Assuming any would be a good fit for your current color scheme and preferences in clothing, here is my vote in order of preference:
1 -
Light sepia
2 -
Dark brown
3 -
Navy blue
Grey is a great neutral that can easily replace black in most wardrobes and bag collections. It and the brown are almost tied, but for the fact that I believe that there will always be a great brown bag that one may ultimately get. Not the same when it comes to finding a great grey bag.
I will say that the blue, while lovely, is not as impressive as other blues that I have seen from YSL or even the current season blue that I'm crushing on from Givenchy. Maybe I need to see it in person to like it more.
Anyway, that's my vote and reasoning. Hope it is of some use.
Good luck!