First pictures - allmost done. Just a little of miliput needed for arming prop. and in the back.
Nice model and details for such a small scale. Just a comment on the warhead which have two "grooves" on the front. This is wrong (I suspect you might have seen a picture of a type 1225 exercisehead, as those would correspond with the dual blowing-mechanism..?).
What are correct colours for this type of torpedo?
Warhead is dark - so it can be red.
I think I will make it "silver" with dark tail and red warhead.
I believe yellow warhead were used for training. For live torpedoes they were unpainted, before greasing a light gray torpedo body & a darker gray on the tail section. After greasing with a dark transparent brown colouring.
Sorry, but you got this wrong...
German G7a (and G7e) torpedoes were made of steel (later, experimental, ingolin torpedoes were made of aluminium). The torpedoes were in general unpainted (ie: models should show a metallic steel finish). Early production G7a's had a nickel-plated the afterbody (ie: a chrome-finish).
Paint would have been used to identify certain variations of torpedoes though (two thin vertical green stripes on the rudder to identify LUT II-equipped T1 or T3, and green painted fields on the aft-section + covering the "S.S." marking on the T1's speed-regulator" to indicate a torpedo without starting-gear and/or a strenghtend engine).
German exerciseheads were painted red and white (horisontal stripes). Warheads were painted grey (some variations to the shade - mostly light, but the T5/T11 torpedoes would have a darker shade). Heads were manufactured from steel or bronze. The latter would sometimes have been unpainted.
As pointed out in previous post, grease was used for lubrication and corrosion-protection, and variants of brown colour would be correct to simulate this on a model.
Propeller on many pictures look's to be 5 bladed - but It's too late to fix it 
Maybe there were propellers with 4 blades too...
Early versions of G7a had 4-blade propellors, but 6-blades was the standard (the G7e had 2 blades, but of course they also didn't have the sturdy "whitehead-tail" of the G7a).
