For the plywood, just use a light brown or tan colour - the wood grain wouldn't be visible in that scale. The instructions are more or less correct for the interior in aluminium; the cockpit was painted, mainly Interior Green, as were the seats, with the cockpit soundproof cladding in a paler green. The seat-back cushions, if fitted, were dull yellow. All fittings such as seats, tables, racks etc, the top turret and the bomb racks were Interior Green, and often the entire bomb bay was also, as on earlier aircraft. Ammunition boxes were wood, so paint as per the doors into the bomb bay. The front bulkhead, visible at the rear of the nose (bombardier's) compartment, was Interior Green, with the soundproofing again in a paler green. If you want to improve this area, cut-out the 'doorway' that is moulded onto the bulkhead, and glue some rolled tissue or similar to one side, to represent the curtain that covered the hatchway. This will give more depth to this area, and emphasise the internal detail. Same with the doors from the cockpit and radio room into the bomb bay; cut them out, and make new ones from plastic sheet or card, posed open.
The 'bare' interiors were introduced on the later production blocks of the 'G', to save production time. Earlier 'G's' had a painted interior, like the 'F' model, and some were painted as far as the radio room, with the fuselage aft of this in bare aluminimum. So, you can vary the interior if you wish, depending on the particular aircraft, which might make it more interesting! The kit represents a late version of one of the earlier production blocks, with parrallel waist-gun positions and standard tail-gun position, so the possibilities are many.