The unusual color code

Going home from college is always fun, no matter how soon we are going to return. The trip to Trichy from our college is always filled with enjoyment. Usually group of friends travel together and they always have interesting things to look at and entertain themselves( i mean the movies that they put in the bus:). As not much people come from my town and because of my unconventional travel time most of the time i am forced to travel around alone. And mostly i do not find those things(like movies) interesting, hence i usually prefer gazing outside the window. And the road expansion going on along the Trichy-Tanjore road has given me a good alternative to look at.

Large machines of any kind have always fascinated me by their sheer size. And this road expansion activity have given me a great opportunity to look at new machines like Excavator, Grader, Backhoe, Roller,Compactor,Tractor-Trailer,Cranes to name a few. By viewing such machines for past 3 years, I have noticed an unusual color code in Tractor unit color. This is not tractor that is used for farming, it is the unit that pulls the lengthy trailers. It is also called as Semi-Trailer Truck in U.S or Artic (short for Articulated truck) in Europe. Here is the color code:
The Volvo units are either in RED color or in a BROWN-WHITE combo color.
The MAN units have YELLOW color.
If u see any units with colors like SILVER, ORANGE or PINK then it is made by Asia Motor Works(AMW).
The new Tata units have RED color.
The old Tata units do not have any "characteristic color" but WHITE and BROWN-WHITE combo are predominant.
The Leyland units(mostly old) do not have any "characteristic color" but the BROWN-WHITE combo are predominant.
And i haven`t seen any Actros Trucks( made by Mercedes-Benz) or new models of Leyland trucks in these roads.