Some info I found via the net ...
"KGV wore at least five camouflage schemes.
There is a KGV class book in publication now, entitled "King George V Class Battleships" by Roger Chesneau (published by Chatham in 2004 - ISBN 1 86176 211 9). Although not as detailed or technical as the superb Raven Roberts book, it is nevertheless a useful book for modelers and is rather inexpensive.
The first two schemes worn by KGV (Chesneau, pg 51):
1) KGV was photographed at Rosyth in October 1940 about to join the fleet in an unofficial, dramatic yet different disruptive scheme entirely composed of Admiralty Dark Gray over Admiralty Light Gray.
2) KGV wore a very sedate, medium gray overall during the Bismarck fight in 1941
The third scheme (Chesneau, pg 51):
3) KGV wore Admiralty Intermediate Disruptive from about June 1942 through 1943. There may be some disagreement on the colors that composed Admiralty Intermediate Disruptive. Vlad reports that the colors are AP507A, B5, B6 and AP507C based upon Roberts' book. Chesneau identifies the colors as AP507C, MS2, B5 and MS1. You might want to check with John at White Ensign Models to be sure. Be advised that the Admiralty Intermediate Disruptive scheme is not historically correct for the Tamiya 1/350 scale KGV kit. The Tamiya KGV kit depicts KGV as she appeared after the major 1944-45 refit. In 1944-1945, KGV and her surviving sisters received a major refit that included the removal of the midships catapult and moved the boats to a new structure where the catapult once lay. They also received an increased AA fit. As I said, the Tamiya kit depicts KGV after the refit and after she wore Admiralty Intermediate Disruptive.
If you really like any one of the first three schemes, particularly the the dramatic Admiralty Intermediate Disruptive Scheme KGV wore in 1942-1943 as many do, you would be more historically accurate to use the Tamiya Prince of Wales kit with the catapult and Walrus amphibian then paint it as KGV.
The fourth and fifth schemes - the most historically accurate for the Tamiya 1/350 KGV kit (Chesneau, pg 51-52):
4) a great wartime camouflage choice for the Tamiya KGV kit is "Admiralty Standard Scheme Type B" better known as British Pacific Fleet Scheme, possibly gray G45 overall with a B20 medium blue rectangular hull panel that covered the armor belt above the boot topping and extended a bit fore and aft of the belt.
5) another good choice for the KGV kit is the scheme KGV received just before the end of the war and continued to wear until the end of her service life: hull painted in standard AP507B medium gray with AP507C light gray upperworks (Chesneau pg 52)."
As far as the painting of the portholes is concerned... When the hull is painted , take a piece of a thin brass wire or a needle with a dull ending ( the diameter both of the wire and needle shold be about the porthole diameter ) . Then drown the wire/needle ending in a paint but a little bit only. Just to take a small drop of the colour at the ending and spill onto a porthole . Please make a test on a piece of white cardboard firstly. You will see how small dots you may get. Just a matter of patience. When all these round windows are painted , use the same way for applying the gloss clear coat. Or you can use a gloss colour. The effect should be the same.