It will be painted in the colours of Königlich Württembergische Staats-Eisenbahnen. Dirk Wenzel provides good information about the colour scheme on this German website of the Württembergische locomotives. The standard book on liveries of German locomotives by Wolfgang Diener:"Anstrich und Bezeichnung von Lokomotiven" is also a good source for paint schemes.
Alas only black and white photos exist of this loco when it was in service, but the German railways used a RAL colour code system, which makes it easier to find the correct colour, even after more than 100 years. My other English locomotives have colours that have names as Brunswick Green, Crimson Lake or Royal Blue: this makes it a lot harder to find the correct colour.
But even with the RAL code system, the colour of locomotives can be slightly different from one loco to another, due to age and weathering of the paint coat or dirt and oil covering the loco. Even my 5"gauge GWR 14xx class locomotive looks a bit weathered after 12 years of service.
The frame and wheels will be Carmine red RAL 3002 (Karminrot), the smoke-box, cylinders, running-board and roof will be Jet black RAL 9005 (Tiefschwarz). The cab and tanks will be (typical for the K.W.St.E locomotives) Black grey RAL 7021 (Schwarzgrau).
As a primer I'm using "Sigmacover 280". This is a 2K epoxy marine primer, used on boats and offshore equipment. This was advised to me by one of our club members, who was a painter in his professional life. It is a strong primer and has good adhesion properties for steel and brass, is relatively easy to use and can be overcoated with most other paints. I'll use a 2K polyurethane paint , "Nelfadur lakverf 2 DN", for the colour coat.
The first step; completely dismantling the loco and cleaning the parts.
The sheer number of parts makes it hard to find space in my small workshop to store everything.
A colleague at our school was willing to give me some instructions on how to spraypaint correctly.
The first stage: primer on the main frames. During this primer step, I also spraypainted the body of a 5" gauge goods wagon my son was building.
The beginning of the final assembly of the frame.
A single pack primer is brushed on the back of all the parts before they are bolted to the frame. This way I hope to prevent corrosion between the bolted components.
The first stage of assembly. The bolted components and bolt heads ready for a primer coat. After this the colour coat can then be applied.
The buffer heads were heated with a propane flame and then dipped in used motor oil. This burns the oil on the metal. This is a simple and quick way to prevent corrosion and it gives an authentic black finish.
One of the small jobs that still had to be done: making the lifting hooks on the roof. These hooks are taper turned from 4 mm stainless steel rod and bend into a curve. They are silver soldered on the curved mounting plate. Afterwards they were cut to size and fixed to the roof with M2 bolts.
The four lifting hooks bolted on the roof. On the real loco these were used to lift the complete cab, for maintenance purposes.
With a small and simple Badger 250 airbrush primer was applied on the bolted components and bolt heads.
The wheels; applying the masking tape took almost more time then the actual spraying.
My son's GWR 'Iron Mink'. It is now almost completed.