Yes, I did get in touch with the V&A Theatre Museum and have just heard back from them. Disappointing news though, as they told me they have nothing relating to Hilda Trevelyan's original Wendy costume, and no idea of what happened to it... Can anyone on this forum shed a light on what happened to it?
But I agree with you - the magic lantern pictures aren't consistent with the greens of the dress (nor the brown/red of the jacket), and looking again at the photos from the play, it does look as though the strips should be the same colour as the jacket. It would make more sense too, as they look as though they're attached to the jacket, not the dress. Go with your instinct!
Going back to Finding Neverland, it's as if they wanted to make Wendy more boyish with her hair flattened than in the original version, perhaps to make her less twee and more appealing to a contemporary early 21st Century audience. Hilda Trevelyan has her hair styled in what the French call 'anglaises', ie tight ringlets. One wonders where Wendy found curling tongs in Neverland ... but then, you have to suspend disbelief out there, haven't you?
Christine