Need to easily create vertex color for ID map baking? Need precise control where the color should be?

Vertex Color From Vertex Groups addon let you create vertex color at a click of button.  total edge control of how vertex color should distribute.

It simplifies the process to a minimum,  and the individual color is unique from each other for easy color ID picking during texturing.

****************** update *****************************

update 1.2:

fix compatibility for 4.3.

in addon preference tab, there you can change the UI tab name. restart Blender to take effect

move the addon panel from property window to 3d viewport side panel

update 1.1.1: 

added a " add prefix to VG" button.    often time, I need to combine multiple object, if some of them have the same vertex group name, the vertex groups would merge together, which may not be ideal.  now there is a button to add object's name as prefix to vertex groups. so that when they are merged, original vertex groups are intact, and their colorID is unique. drag select multiple objects and press button to apply the prefix.

update 1.1:

improved coloring method. reduce to two buttons.  smooth gradient vertex color and sharp edge vertex color.