Well, the accepted wisdom was that it started out white, then went into silver, then "Raspberry Ripple" and finally hemp (after it was grounded). I never doubted any of this as photos support that story, but the photo I posted above does clearly show that it was painted before the all-white scheme. The problem is that a black & white photo doesn't clarify anything. Instinctively, I'd assume it was painted in yellow primer, but I've heard various people claim that at least one former Shorts employee insists it was fluorescent orange.
I'm still not convinced, as it seems unlikely that it would have been painted orange and then repainted so very swiftly in white. Seems like a very expensive proposition. Plus, it seems odd that there are photos of the aircraft in every guise, but not orange. And of course primer yellow would be a far more logical colour in any case.
On the other hand, one recalls that the RAE's Javelin was painted overall fluorescent orange, so it's not such a wild idea... and the photo does look very like the way that fluorescent orange looks in black & white. I suppose the key to this story is just how reliable the "man from Shorts" was/is.
So, the mystery continues!