Here is my two cents worth of advice: (This is my approach)
1. Try to pick a color for the outside that you'd use all of the time if it were only a one color bag.
2. Then, pick the leather that makes the color look best to your own taste.
3. Next, pick the hardware color that looks best with #1 and #2.
4. For the inside lining, pick a color that you really like/love but wouldn't necessarily carry as bag if that color were on the outside. (I think that's why a lot of H fans pick colors like Rose Shocking, Soleil, Vert anis, orange, and so forth.)
5. After you are set on #1, #2, #3 and #4, you are almost done with your SO. Now, you need to visualize how the bag would look if (a) only the inside lining was a contrast color; (b) the inside lining and the outside piping were contrast colors; (c) you like the look of having the handles be a contrast color; (d) you like the look of having the front straps be a contrast color. My suggestion is to use colored pencils (or crayons) to sketch out each option to give you a better sense of what each would look like.
6. After you're comfortable with your decision, then you go to your SA, tell/show her what you're leaning towards and ask for her opinion.
P.S. Oh, and you should know what size you're looking for. I use mine as a tote so 35 is more practical for me.
such wonderful advice! thank you