As Tom suggested, Joachim, Krylon is my choice as well.... HOWEVER..... It appears that Krylon is starting to change the consistency of some of their products. So far, the Acrylic Crystal Clear Gloss, Satin and Matte are still availble in the old cans. Test the compatibility of the can on the bottom portion of the locomotive to see how it adheres. Use the Matte can # 1311...
There are different Krylon materials for crafts. Suggest you don't use those. I get mine at Wal-Mart, Ace or Tru-Value Hardware. Home Depot or Lowe's does not carry Krylon in our area.
If that works OK, them mask the windows and start with light coats followed by slightly wetter. Do avoid applying too heavy to avoid sags and runs...
I live in Germany and I am afraid that I can not buy Krylon. But from Stan's answer I have learned that Krylon is an acrylic based paint, so I guess that the original Aristo color is also acrylic. I will try to find a matte acrylic spray paint to do the job.
Any hobby acrylic should work, although they're generally more expensive.
I've used Tamiya, for example, on military helicopter flying helmets that got banged around, frozen, baked in the Sinai sun, and showed hardly a sign of wear and tear over several years. Paint and protective clear-coat were both Tamiya. Almost without exception, any bumps (like the front doorpost of the Kiowa that I was flying through the 1980s and early 1990s - it was cramped in the cockpit) took paint off of the other surface and left streaks of it on the Tamiya.
Some acrylic sprays have UV protection, which is an obvious benefit. The Tamiya paint made no mention of that, but never seemed to fade. Back then, one could only buy clear gloss and a separate matting agent that had to be mixed in. I'm not sure if they offer matte pre-mixed now.
Where in Germany? I was in Lahr (Schwarzwald) from summer 1986 to 1989 - and never wanted to leave.
First; exact paint matching is generally a 'lucky fluke!'
The manufacturers have large batches mixed, and it can be special paint.
HOWEVER that does not mean that you cannot try. For that I suggest that you use the acrylic paints, as opposed to enamels as they dry faster, and are easier to mix, as whilst drying there is less of a color shift.
The easiest acrylics to buy are the 'craft ranges' Bear in mind that you are painting over black, and orange is a very thin color (being made from yellow & red, both notorious for being poor covering power colors. Undercoat the area intending to be orange in either white or a very pale grey. At the same time do some scrap styrene plastic card; this is your 'try out' piece.
Now mix orange (& white which will be needed as the orange I have seen is not as light as Milwaukee road orange), and try it out to see what happens when it dries. The you can mix the color for applying to the loco, and put it on. When it is dry add a matt varnish, these are well known for not drying matt, a tip, add a very thin wash of the same color mixed in the the varnish (in this case an acrylic varnish) + some windscreen washer, (about 10% by volume), fluid (ignore the color) to allow the very thin mix to spread out and not bead up which it will do without the wetting agent in the w/w fluid.
A final thought; color is never static, it is bleached by the sun (and goes lighter) in the case of orange - it goes chalky and thus lighter), and gets darker by smoke pollution, which can dry in dark(er) streaks, then the rain/snow gets at it and can strip varnish and layers from it. So it does not have to be exact as such things vary the color. I am not suggesting a fully weathered version, but the color does get changed.
Milwaukee RR orange started out quite dark (on the Hiawatha's) but seemed to go lighter as time progressed, but that could be the from photos, and the light in which those photos were taken, and the time of year as well.
Of course in the end the Milwaukee was taken over the that 'Big Bad Bird' of Union Pacific, and they used the constituent colors of orange, being yellow & red!
Many thanks for the information. I have located a couple of suppliers of MILW orange but as you will guess the postage is somewhat in excess of the paint cost.
I think I will get acrylic paint and experiment with mixing until I get the color which is nearest, when dry, to my MILW locos. I have a clear cote which I can apply as a finishing coat for durability and handling.