Why heavy equipment is painted in yellow?

Any mechine or equipment opreated on high risk with in the area of accidental zone  need to be painted in yellow as it is very shining colore and very much visible in dark also.

Yellow being a color of contrast, making the machines in this color stand out to the eye.

As far as safety concern yellow color known as precautionary due to this we have seen most of the equipment are in yellow color. Color also depend on the machine capacity.  

Heavy Equipment and machinery are operated in risk area/Location it should be visible to the people surrounded / working should be careful  avoid accidents yellow color is used. 

yellow paints reflect s in the power in case night time easy visible

even though in dust or mud looks bright

heavy equipment is painted yellow to contrast between the machinery and the surroundings so that people keep a safe distance for safety reasons

For Safety purpose as yellow color have more visibility 

Because Heavy machinery is painted yellow to show caution. Yellow is used because it is bright and eye-catching .  Heavy machinery is painted yellow to show caution. Yellow is used because it is bright and eye-catching.

yellow is the color people most often associate with amusement, gentleness, and spontaneity

Yellow is painted to enhance visibility and to serve as a warning to people nearby However, it is not a legal requirement. 

Reason is very simple,yellow color is shining and therefore is more visible which makes higher safety attention.