Even with overcast there can still be fading from ultraviolet radiation (
http://www.loc.gov/rr/scitech/... and
http://www.epa.gov/sunwise/doc...). If the cloud layer was thin (overcast but not deep clouds all morning), fading from UV could have been a culprit. If that's the case, it wouldn't seem unexpected that the pale pink/mauve of the hybridizer's description (in which it is blended with yellow/tan) might have "photodegredated," leaving only the yellow and paler tan highlights. Is that on the right track, that it might have been a hazy overcast, and not deep layers of cloud?
Of course, there also could likely be plant genetics, chemical soil components, heat, etc., at play that might have produced some change or fading of colors from the original cultivar. Catcher in the Eye is one that seems described one way, photographs another, and in my garden is a very different color than most pictured (but matches the written description). And, then there are the changing colors I saw on a recent cultivar's scape of blooms, one pale lavender, one pale pink, one yellow, and one near-white. Mysterious, but fun to ponder.
