I think as far as Prince of Wales goes, my personal view is that there isn't any B5 or B6 on it. I personally have read one genuine wartime report on Prince of Wales' camouflage (observation trials) and it described only its categorisation of Admiralty Disruptive pattern. It didn't record the colours.
Unless someone knows better, I think any notion that it had B5 on it came long after the war when people trying to interpret the legacy images already had an incorrect understanding of what B5 was.
For example, had I mislead my daughter from her earliest years by telling her that grass was orange, and that any time she saw the colour green I told her it was called orange, then when I asked her what colour a lime was, she'd tell me it was orange because she had the name attached to the wrong colour.
There are plenty good quality images and film stills of smaller vessels, landing craft, coastal boats and so on (even King George V is well photographed) which are so obviously in B5 or B6 that we know that when B5 or B6 were genuinely present we really can't mistake it. That colour still of Prince of Wales has lots of grey on it. One grey looks slightly bluish compared to the others which look warmer, but that doesn't make it B5 in my personal opinion unless the B5 were so heavily chalked and faded as to render it almost unrecognisable. I think the bits we've been told are B5 were actually Home Fleet Grey. I think it only looks bluish because the warmer, lighter greys are MS3 and MS4a. Also there's a bit of psychology involved. We've got a preconceived idea now that B5 is there so we're looking for it and trying to peg the name to whichever colour looks most like it - regardless whether that colour far better fits that which goes by another name.
Unfortunately the collective "we" also think MS4 and MS4a are also quite strongly coloured. The ones I saw at Kew aren't - they're rather non-descript light greyish shades. They're not completely neutral, but they're not strongly coloured either. Neither are the ones Richard matched for me at Portsmouth.
Furthermore, 507C is a touch darker than we have understood, so in reality it was darker than MS4a, but the colours we thought we knew until recently have this the other way round.
When this is all over, I reckon we will agree that HMS Prince of Wales was wearing something more like white, MS4a, 507C (or maybe MS4), MS3, 507A and MS1 than the schemes we see prescribed now including B5.
As for which colours are suspect still, the truth is that they're all being considered but that we have more confidence in some than others. As a general statement, anything you know now that is yellowish I am suspicious of. We have lots of greenish blues that should be blues, and we have warm greys that should be neutral. This is not too far from Luftwaffe colours really - for years modellers have thought of RLM65 Hellblau as turquoise based on some decades-old relics and celluloid test cards known in the 1940s to yellow within a decade. When Jurgen Kiroff gathered the real recipes, original pigment types and original machinery used to make the paints he recreated them all and lo and behold, the typically impassionate German description "Hellblau" was given to a paint because it was light blue, not a turquoise. It's disappointing how much momentum these fallacies gain really. If Hellblau was turquoise the Germans wouldn't have called it Hellblau. The pigments were also known for years - any idiot could tell you white and ultramarine mixed together will give you a light blue, but because someone dug some wreckage out of a garden and matched it, the world now thinks RLM65 was turquoise.
I'm ranting a bit now
Off the top of my head, ones I still want to verify or update include:
B6
MS4
MS4a
G20 (it matches Portsmouth's sample very well, but there's something we don't fully understand yet)
B20
B30
G55
B55
There's also a 13% LRV version of Home Fleet Grey coming out soon as a new colour not replacing anything existing, but rather to allow the modeller to choose the look they want where the original paint was 507A or 507B (or pre-made matt paint bought in to be completely correct).