YYs are not my area of expertise, but I do have some knowledge of sunfades.
According to the second post
here, the normal grey will fade to pale blue. Having said that, I would add that completely even sunfades are unusual (but not unknown)and, in my experience, Lesney sunfades have a tendency to look slightly dirty, sometimes with an almost mottled experience.
This model seems to have an even colour all over with the possible exception of the back half of the undersaide of the rear leaf springs (or is that just dirt?). These should be investigated further. I would also suggest that comparison of the overspray pattern on the inside of the bonnet with a normal grey example might pay dividends.
Please note
this thread discusses a further example.
