im a bit bias (check my profile pics
), but id say go with the ink!
when i bought my messenger, i originally wanted to buy it in black, but barnyes only had it in olive, ink, and truffe, and i went with the ink, no second thoughts, no questions asked. its really such a beautiful bag, and besides on these forums, you'll never see anyone else besides yourself with this bag, in this color
also, ive seen some gorgeous olive bags on this forum, but i dont think it works really well on the messenger having seen it in person next to the ink, where as ink is IMO the perfect color for this bag!
here some pics of my ink, the first one is when i got it, the second is a picture after its aged and been put to use: