hi ya Barry
and everyone in the World, sadly and very sadly this model wasnt built by me and it doesnt belong to me – it is housed in the Maritime Museum in London and I believe the builder is unknown – all I do know it wasnt me hands up 
Right Barry, to get back to the colour shemes of these vessels; I have built several RAF Rescue Launches namely The Whaleback and also the Vosper 73 foot one and when I was building these I was in touch with 2 or 3 people one gent, Christian Shepherd – I dont think he comes onto this forum though – but he does go onto Mayhem and I will send him a link to this Topic. Christian has a wealth of knowledge and is very helpful with these type of craft.
The 2nd guy is an Australian, and for the life of me cant think of his name I cant. He actually served on Rescue boats & he was based around the English Channel and when I questioned him about the colours of the vessels – this gent and Christian both came up with a similar reply – basically in the very early parts of War 1939 to about 1941 the majority of the boats had a bright yellow painted deck and superstructure. But, they came to realise that this made them too much of a sitting target for enemy aircraft and also some friendly aircraft used to use them as target practice. So, the colour scheme of the bright yellow deck eventually was faded out where only certain areas like the tops of cabins were yellow and then it was towards the latter part of the war it was phased out altogether and just a general grey scheme was applied. Also, for recognition you will find from about 1942 onwards these vessels began having roundels painted on the deck and also a red and white chequered area along with a radio call sign painted on the deck. This was to aid friendly aircraft in recognising the vessel.
if you can get hold of model boats mag, JUNE 1982 you will see there is an article, and a set of plans by John Pritchard covering the 67 foot ThorneyCraft Launch. I have several black andc white pics of these launches stowed away on a disc, asthis is one of my planned model builds. So, give me time and send me your email address in a personal message and I will email them to you – as well as sending Christian a link to this topic.
aye John