Every once in a while a reality check is good though. When the carp seem to want something small and subtle I usually go straight to a Hare's Ear Nymph. If I was good enough at keeping a journal I might even find that my most productive carp fly of all time is the Hare's Ear in multiple variants.
I have caught Carp on many different recipes of this infinitely flexible nymph pattern. Throw in a gold bead and you have a weighted fly with a little flash. Add a black tungsten bead and you are ready to dredge the depths. In colored water sometimes adding a flash-back can't be beat. Do you really need a little bit of that carp-specific luvin feeling? Some fine Rubber legs do the trick. Are the fish ultra-shallow and super spooky? A very simple un-weighted variant in natural colors without even gold rib could be the ticket.
I usually stick to size 10 to 14 and my most productive colors have been olive and the traditional tan.
The Hare' Ear Nymph. It turns out that nearly everybody has a couple carp flies in their box!