Camo Paint scheme for the Mosquito FB VI from Banf Strike Wing

From the excellent Modellers Datafile by Richard Franks, backed up by a colour photo in RAF of WWII in Colour, I concur with Quincy. Initially they would have kept the schemes from other units. Toward the end of the war 143 sqn moved to Dark Slate Grey and Ocean grey over sky with yellow spinners with a Medium Sea Grey tip.
Demarcation on coastal strike mossies was low down on the fuselage.

I've got a couple of sources which have pictures of (supposedly) Banff wing Mk IVs and both pictures are grey over grey (one base Flight w/slipper tanks and red spinners and one from 143 Sqdn w/rocket rails and white or sky spinners). Having said that, I wouldn't rule out the Squadron example as being inaccurate. It's more than likely that when the unit first became operational, they used grey/green over grey as issued - the powers that be aren't going to let you shut down operations to paint your aircraft - they get painted on an individual basis, usually when they go in for major repair and/or major phase inspection. It happened in every Air Force which fought in WW II. As long as you have documentation, just pick the scheme you like best.