Sorry. ;D
Here's a blowup of the newest hi-res shot --
It's definitely mid-painting, but it could just as well be the first painting after the war if it's closer to 1949-1951 (I've seen Frith dating that's even worse than that). A lot of other boxes show this kind of very pale colouring after the war from extreme fading and wear due to the poor maintenance from about 1939-1949 or so. Paint was considered a vital war material and pretty severely rationed even after the war from what I understand.
Or it could have just been stripped to the concrete before painting as
Mark suggests. Regardless, looks like the top and front took priority as they already have a full coat on them. Based on the shade of grey, it still looks to be a medium-light blue, possibly a bit darker than the pre-war blue, but quite possibly the same. After all, the 'Genevieve' Box in 1953 looked to be relatively newly painted yet had about the same shade of blue as the 1938 colour 8mm footage of the Cambridge Park Road Box, which was only a couple years old at that point.
Going by the new Box colour compared to the top sign flood colour, it does seem a bit darker than the pre-war as they are almost the same shade here; however, the signs kind of look like they might be a bit faded as well - not the usual darker tone. If they haven't been replaced since before the war, then it wouldn't be an accurate gauge as they are also subject to fading, as we've seen elsewhere.
EDIT:
Then again, take a look at this desaturated version of the "Genevieve" capture --
Looks to be almost identical, right down to the only slightly darker signs. This suggests it might have looked about like this when fully painted --
Here's the 1938 shot of the Cambridge Park Road Box for comparison --
Considering the faded condition of the film, it was quite possibly about the same colour.
