Do you plan on buying additional Hermes bags in the future? If not go with a neutral like Black, Gold, Etoupe, or one of the browns.
However, I would suggest you look at your wardrobe and see what colors you wear the most ( other than black and white)...and perhaps buy a bag from that color family. You know you will use a bag in color if you buy one in a color you love and wear often.
I've same problem with you. Can't decide which color and size. With help from our friend at purseforum, I decided to buy Birkin Togo 35 Mocca. It's neutral and beautiful. Since it'll take me sometime to buy another Birkin, I decided to buy neutral color that support my whole wardrobe. Just another thought for you.