So to use it with regular instance you just have to convert your instances to an instancer.
It can be done by script using the "emit" command to create particles at each instance positon, write attributes and attach an instancer.
But I prefer a better/simpler way, using some nodes coming with the SOUP plugin for Maya.
SOUP is the best plugin ever for Maya and is free : http://www.soup-dev.com/tools.htm
SOUP basicaly adds nodes to Maya to use the same workflows as in Houdini and a lot more, also have a bunch of amazing tools.
Converting instance to instancer is done like this: Then as now we are using an instancer instead of regular instance the Octane randomColor node just works:
Also you could just use from the begining, the SOUP InstanceManager tool ,
you would have instancer for free without dealing with nodes, and one of the best scattering tool existing for Maya.
