Equipment from "outside" suppliers were often painted different colours throughout the war. A standardisation was brought in to use in very early 1944, but due to stockpiling you would find late war vehicles with different colours for the drive train, gearbox etc.
Engines were mostly RAL 7016 but you could find some engines that were built early in the war painted in RAL 7008 with many transmissions etc the same.
May- September 1944 saw the interior colour change from RAL 1001 to RAL 9002. This is due to a series of raids by the 8th air force on chemical and paint plants reducing stocks, output and supplies. The paint used was actually the same colour as the Kregsmarine S-Boat hulls known as Schnellboot Weiss.
What you have to be careful of is the "scale Colour" paints made by AK and MIG etc. they do not really represent the true original chipset colours used, which OEM paint companies actually managed a +/-10% variance of the colours, which is not noticable to the Mk1. Eyeball, throughout the war, air raids, supply disruption and shortages etc. A truly remarkable effort!
this is why I use Vallejo as they have a chipset accuracy policy and I do like the way their paints go on.
Interior fire extingishers were red, while ones mounted on the exterior were black. you don't want your vehicle spotted because of a bright red object hanging on your vehicle!
Another colour was RAL 6006 Feldgrau Nr.3. Used to paint ammunition boxes and equipment throughout the war. quite often you would see tank radios, electric junction boxes etc in this colour.
James