I'm with Wojtek on the oil tank. Tamiya probably got the colour from a preserved machine. As far as I know, the tank would be silver painted, but might have had a reddish brown anti-corrosion coating also. The part F1 is a landing light. They mean paint the INNER face silver, so that it looks like the reflector when viewed through the lens. If you really want it to look like a lamp, attach a piece of kitchen foil, using clear varnish or Johnson's 'Klear' or, if you have it Micro 'Krystal Kleer' or Humbrol 'Clear Fix'.