revell 1/32 supermairine spitfirer mk.1

If what you're talking about is in the back of the seat, behind the headrest, you're referring to the voltage regulator, which were not always present.  Bottom line, check with the reference of the aircraft you want to build.  If that's not the component you're referring to, my apologies.

On that thought, the radio is directly behind the pilot's seat, about under where the fuselage roundel (port side) will be placed.

no thats the one anderww ..thanks

i,m building it with out the voltage regulater ..ur right on that some had it and some did,nt ..found two pit photo,s showing just that ..agian thanks for ur input anderww..cheers

You're welcome.  I recently did a 48th spit with an aftermarket radio inserted.  The colour callouts were interior green for the framework and canvas on the radio.  I did a little reading, the radio was sometimes covered in canvas or almost a waxed paper to protect from moisture.  I guess otherwise a metal or black colour wouĺd do, depending on the detail the kit gives.  I know my resin bit looked like a bundle of cloth.  Hope that helps.