You can download it from here.
In order to use it you have to put it in the nodes directory of your Animation Nodes Folder.
On Windows for example that would be in the following folder (replace USERNAME with your user name):
C:\Users\USERNAME\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\animation_nodes\nodes\mesh
Titel: Animation Nodes – Vertex Colors Node
Sprache: Python
The Vertex Colors Node is an extension for the Blender Addon Animation Nodes.
It allows the user to change the colors of each individual vertex color as opposed to the standard vertex color node which only allow the user to give all vertices the same color.
Animation Nodes is an Addon by Jacques Lucke. It can be found here: