HMS Severn camouflage

[1200ships]

I have attached three images of HMS Severn that I downloaded from a Russian naval discussion board, although do you think I can find them again now. Anyway, they show the submarine in an interesting camouflage scheme, and I would like to ask your help in deciphering the colours used. The shots show her in, I think, Dundee, (can someone confirm this) and were taken in the early part of 1943. This is based on the presence of the destroyer HMS Scimitar in another photo I have taken at the same time. The two ships were only ever in something like the same place in early 1943.
The saddle tanks look to be painted in black, with the hull casing in Home Fleet Dark Grey or equivalent. It's the conning tower that is confusing me. It has a pale base, with a medium tone pattern painted on top, but the pennant number is in an almost identical tone. Assuming it is supposed to be readable in real life, the pattern and pennant are probably different colours, but what?
My current thinking is the tower is painted in white, with an overlay of B30, with the pennants in some sort of medium grey. The numbers could be colourful, but the tone does not look dark enough for a red or green, but they could be blue or yellow, with the pattern in a medium grey. What are people's thoughts?

[SovereignHobbies]

How early in 1943? If it's before May, these are highly unlikely to be B&G series colours.

Have you seen this image of HMS Surf in what is captioned as 1943, but I think that's HMS Forth behind it wearing the same colours as those very evident in the IWM's collection of photographs titled "Aboard submarine depot ship HMS Forth, Holy Loch, Scotland, 1942"
https://www.flickr.com/photos/8270787@N07/17334075225/