Well, there's Khaki Campbell and there's Dark Campbell. Dark Campbells have dark pencilling (lines) on their feathers. Overall they appear much darker in colour than the Khakis. The difference is that Khakis have a brown dilution gene that makes them much lighter, plus ideally they should be a much more even colour overall. The brown dilution gene is sex linked, so females have one dose and males have two doses.
Basically, with sex linked colour genes, you need:
1. A male with a double dose (homozygous) of the recessive version of the gene (carried on the Z chromosome, of which drakes have two, so that's how he can have two doses of the recessive gene) - i.e. a Khaki Campbell drake
2. A female with the dominant version of the gene (as it is carried on the Z chromosome and she only has one Z chromasome she will only have one dose of this gene) - i.e. a Dark Campbell hen.
All the female offspring will be Khaki Campbells. All the male offspring will be Dark Campbells.
Edit - I am really sorry to hear about your duckling. All is not lost though. Birds can heal up very well from injuries. Does she need to see a vet?