On a few shots I took of a peahen at my zoo, I saw something like an irridescent greenish-blue colour on her tail, don't know if that's what you saw, though.
P.S : She is the regular Indian Blue Peahen, so yes, this is only the feather under the sunlight that has this colour, I believe and, depending where the light's coming from too.
Then again, I don't know if that's what you meant. xD