Are Khaki Silver Duckwing the same as Fawn Silver Duckwing?
No, Khaki is to Fawn as Splash is to Blue. You will get a certain portion of Khakis from breeding Fawns just because of how the gene works. Basically, if your bird carries one copy of dun (I^d / i+), they are Fawn (or Dun, depending on the breed, but it's the same genetically), and if they carry two copies (I^d / I^d), they are Khaki.
Here's one of my Fawn Silver Duckwing boys and one of my Khaki Silver Duckwing boys as a comparison. The Khakis do have a faint hint of a sort of brownish-gray off-white to the parts that the Fawns have brown, but it's hard to see unless you're looking closely so they mostly just look white.
Khaki Silver Duckwing hens are a little bit more colorful because of the touch of salmon in their chests. This is a Fawn Silver Duckwing hen and a Khaki Silver Duckwing pullet:
Sadly, those are the two girls that a hawk got, so I no longer have them here. Both boys are still around, though, of course.