The first Disney monorail (now known as the Mk I) ran in 1959, at Disneyland in California. Two years later, the monorail "ride" became the monorail "transportation system" as the original loop track was extended to serve as a link to the Disneyland Hotel, across the street from the park. At this time, the original two three-car trainsets were modified. An additional car was added to each, and a third set was built. These became known as Mk IIs. Each train was painted a different color. The original two Mk I sets were painted red and blue. The new-built Mk II set was "Monorail Gold" (closer to yellow, if you ask me). Each train was officially named according to it's unique color. The blue train was "Monorail Blue", the red train was "Monorail Red", etc.
In the 1968, new equipment replaced the Mk II trains. The Mk III trains had five cars each, and more window space in each car. There were four MkIII trains, three wore the same colors as the Mk II sets, while "Monorail Green" (painted a dark "pullman green") was the newcomer. Other than the above mentioned differences, these three models were relatively similar. They all had the same "Buck Rogers" styling that included prodigious amounts of stainless-steel trim and corrugated sheathing.
All Disney monorails use the " Alweg" system for their running gear. The weight of each car rests on two large rubber tires, that run on the upper surface of the concrete beamway. Four smaller tires are mounded in the "skirt" of each car, and run along the sides of the beamway to keep the train on course and upright. Propulsion is provided by 100 HP electric motors, also mounted in the skirt, which drive the load-bearing wheels, through right-angle gearboxes. Each car draws 600 VDC current from two contact strips, mounted low on the side of the beamway, through wipers mounted in the skirt.
The next generation of Disney monorails rolled out not too long after the Mk IIIs. However, the Mk IV trains were far different in appearance. Gone was the stainless-steel, and in it's place was a smooth white shell, in what was described as "the NASA look". Built in 1971, for the then new Walt Disney World park in Florida, the design was influenced by an encounter between the project engineer and a Learjet, at an airport, in the late '60s. Each Mk IV car had four separate doors per side, and four passenger "compartments" (isolated seating areas, though the interior of each car was open) each seating 10 passengers. The end units also had an extra door for access to the cab. Unlike the small number of trainsets needed to serve the California park, there were 10 trainsets built for the Florida location. Each was identified by a colored stripe, that ran down the side of each car. The colors were, Black, Blue, Gold, Green, Orange, Pink, Purple, Red, Silver, and Yellow.
The Mk V monorails were simply a refit of the Mk IIIs, with new NASA-look bodies. The old running gear was mated to new control systems and body shells, built by Siemans, in Germany.
The Mk VIs were all new replacements for the Disney World trains. Built by Bombardier, in 1989, these were similar to, but slightly larger than, the trains that they replaced. The easiest way to tell the difference between the Mk IV and Mk VI equipment is by the doors , and the rooftop strobe lights . The newer trains have only two passenger compartments per car, and two pairs of doors per side. However, since the new layout allows for standing room, each car can carry 60 passengers, instead of 40 in the Mk IV. Also, the Mk VI doors are power operated, whereas an attendant had to open the doors of the Mk IV trains by hand, from the outside. For the strobe lights, the old trains had a fairly large housing atop the cab, which is absent from the newer equipment.
There are 12 of the Mk VI trains, (as represented on this page) and apparently they couldn't come up with significantly distinctive colors for the extra two sets. They were named "Lime" and "Coral", with stripes easily confused with "Yellow" and "Pink" respectively. They can be identified by white "wings" at the center of each car, breaking up the continuous stripe.
Here are all 12 Walt Disney World monorail trains. My Traffic library contains additional images for right-of-way (beamway), operating doors, and the rooftop strobe light.