2005 Gray or 2006 Lilac 2006 Work?

They are both wonderful neutrals, and would match a similar color palette. Depending on what colors you tend to wear, I guess... grey would be more neutral and match beige as well as black, and lilac would be good if your wardrobe has any pastel colors in it.
 
I would have to say gray 05 since I'm not a big fan of lilac, (but it's a pretty color, just not for me) and because the 05 leather seems so smooshy. I hope I can get a bbag from 05 (or earlier) one day!
 
i know you have chosen a colour, but i have to say this: lilac! :P if i have unlimited funds for bags, i would get both - i prefer the greige rather than the dark grey.