Corogard was a protective treatment on the leading edges of U.S. Navy airplanes at one time. For background, see http://tailspintopics.blogspot.com/2012/01/corogard.html
I was recently asked a question about its applicability to the A4D (A-4) Skyhawk. There's no question that it was initially part of the production paint scheme as shown on this early A4D-1.
It's pretty obvious on this reserve A4D-1. Note that the vertical fin application is narrow and doesn't appear to extend onto the dorsal fin.
However, this YA4D-1, circa 1956, doesn't appear to have any Corogard on any leading edges although the gull gray appears to have been wrapped around to the lower surface of the horizontal tail for a short distance (and probably to the aft edge of the bottom of the wing slat as well).
In some cases, the squadron trim color was applied to the leading edge of the vertical tail with no Corogard evident and even the wing leading edge in lieu of Corogard.
However, the benefit of the Corogard revealed itself as on this A-4C's vertical fin.
The A4D-2 on the left clearly has Corogard on the wing leading edges and the vertical fin leading edge. The one on the right (from a different squadron) may or may not have Corogard on the wing leading edges (in addition to not having the slat wells painted red) and the leading edge of the vertical fin is mostly yellow, the trim color of the second squadron.
As time goes on, Corogard is increasingly not obvious, if present at all, on the wing and horizontal tails but there is always a wraparound of the top color onto the bottom of the leading edges. But then there are these two A-4Fs from different squadrons on Bon Homme Richard...
I await comments.