That's looking the biz Wayne.
This pic, taken at Duxford, is close to WW2 standard. However, I've just checked a few colour pics from the period, and the variations seem to follow the period in time, although this is not definite. The dark reddish brown leads would be correct for all ignition leads, and I've seen this colour on a Lancaster's Merlin. It's possible that these were fabric sheathed, and the pic dates from late 1942. (at one time, this was a 'standard' identification for all car ignition leads in the UK, up to the mid 1970s at least. After this, 'modern' and 'racing' colours appeared, such as bright red or orange. It's probably connected with domestic electricity wiring colours, where dark red was always 'Live'.)
A Spit shown a little later appears to have black leads, with the guide tube in a silver grey colour, whilst later still, another Spit IX, or possibly MkVIII, appears to have screened leads, with a silver grey sheath colour, and the guide tube may be the brass colour shown in the attached pic - hard to be certain as it's in shadow.
I think maybe the silver grey would be fine, if only to provide a little contrast.