So to the body. I started with a test run of the lower saloon with opaque windows and entranceway to check that the shape was reasonable.
This corresponds to K502 as it is currently presented, but as I collected more photographs it was clear that these vehicles had over their lifetime at least two different body types, and three different colour schemes (and probably many detail differences). The bodies originally fitted were very box-shaped, with their sides going straight down to the floor. They had just three windows in the front bulkhead. In the mid-1920s, after the introduction of the NS-Type in 1923, K-Types (and S-Types) received new bodies in which the rocker panels, the lowest segment of the body sides, were curved inwards towards the floor, improving on the somewhat clumsy appearance of the original design. Also the front three windows were augmented by toplights, improving the internal illumination.
In the original paint scheme, the rocker panels and corresponding bottom panels at the rear were brown, edged in black and with off-white lining. The panels bearing the "General" fleet name were red also edged in black, with black lining in three sections, and with the corners embellished with scrolled decorations. Similar lining adorned the engine cover, dashboard and upper deck sides at front and rear where they were not covered by advertisement boards. The window surrounds and corner posts were off-white. This style can be seen on the restored S-Type S454.
Around the time the new bodies were fitted the rocker panels were changed to red, unlined. The lining on the engine cover, dashboard and upper deck was dispensed with, and that on the lower deck was simplified with a geometric pattern in the corners. This is the condition currently shown on K502.
Finally the remaining lining was omitted, leaving plain red, as seen now on K424.
Just because I rather liked the brown/red/white livery, I decided to go for a version of K502 but in something like its original condition. This may lead to some anachronisms with the advertisements and route information, but I don't mind too much.