I know HMS Hood was in 507B and my WEM tins have B5 and 507B pretty much identical.
Here is HMS Hood and it does apper lighter in 507B than what we are saying B5 is on HMS Prince of Wales:

More images I have found with paints according to Raven:
HMS Cleopatra in MS1, B5, B6 and MS4a


In this we can see MS1 and B5 at the bow. I think that B5 in this instance does have a tone dark enough similar to what we find on Prince of wales.
Here is one really good one of HMS Kent in MS1, MS2, B5 and 507C

I can clearly see 507C right at the stern followed by MS2, immediately after that is B5 (very faint) and right after that is a tiny patch of 507C before MS1.
HMS Trinidad had MS1, 507A, B5, MS4 and MS4a

In this case MS1 is right in midships with B5 supposedly the dark patch at the stern surrounded by MS4 which is making MS4 look likely for the ligher shade of POW as B5 stands out in the same contrast with MS4 as it does in the POW photos. 507A is supposed to be the dark patch forward on the hull roughly below the bridge structure.
Another photo of HMS Renown with what is supposed to be MS1, B5, MS3 and 507C

Like Prince of Wales it does show a similar contrast between MS1 and B5. Again on the hull below A turret this next photo is supposed to be a patch of B5

Also some better photos of POW in Singapore - you can note at the bow here if it is MS4 and MS3 then they are almost indistinguishable:

You can still see the pattern there and I think this is a better exposure of the ship.











