To start, if you have Maya X installed, right click on 
and choose Randomizer
.
If you don’t have Maya X, you can find vertex color randomizer in X-Ray shelf 
click to open.
From left to right.
Applies a random vertex color to every selected object.
Applies random color to select object vertices only in specific channels.
Applies random alpha to select object vertices.
we can say that it will remove vertex color.
from here you can apply specific color to vertecis of selected object.
multiply alredy existing vertex color by custom color.