No worries Charles - unless you can easily over paint the darkest colour, don't change it if it's going to cause problems.
The reason the MkV float plane probably looks different, especially in B&W photos, is that it was painted in the two 'maritime' colours, Dark and Extra Dark Sea Grey, which tend to blend into almost one tone. The 'normal' Spit camouflage was the Dark Green and Dark Sea Grey (Ocean Grey), as shown in the profile Andy posted, which gave a distinct demarcation between colours.
Andy posted the profile just for the pattern, which would be similar, and not for the colours. Once it's all done, and especially with a finishing coat of clear matt varnish, any deviation in the pattern will hardly be noticed with those two particular colours.