Install from file, places it into a folder, which doesn't work since it's missing a __init__ file(I think) I just tried it, if you place weight color.py in Users\Username\AppData\Roaming\Blender Foundation\Blender\2.78\scripts\addons (Restart Blender/Reload Scripts) then enable the addon, it shows up.
I found these addons that fit what I am specifically trying out. https://blenderartists.org/forum/showthread.php?290390-Weights-to-Vertex-Colors-addon&highlight= https://github.com/chebhou/Weight-and-Color Unfortunately, it seems they don't work with the latest Blender version? I tried copying the addons to the scripts…