Khaki is neutral so I'd say it depends on your top/jacket--I wear khaki with a number of different colored shoes (black, brown, etc. . .) depending on what's on top!
I agree. Both black and brown work (much like with jeans) it just depends on what's on top. If it's a lime-ish green top, I'd more than likely were brown (unless it's my lime-ish top that I wear over a black cami, then I'd wear black).
So you see...I'm not much help afterall
There is no value in life except what you choose to place upon it and no happiness in any place except what you bring to it yourself. - Thoreau
I say black with a lime green shirt. And I second the poster who said that khakis are like jeans. Even though jeans are blue, you don't wonder if what you are wearing on top matches blue Khakis are neutral. Just picture what shoes you would wear if you were wearing that shirt and jeans, and wear the same thing.