Hi, unfortunately it's not possible to generate multiples IDs from a Forest object. Both Max and VRay see it as a single entity, with its own object ID.
As far as i know, we cannot modify vertex colour or other channels from the plugin either. These channels are handled internally by V-Ray.
But as workaround, you would use Forest Tools to generate stand-alone instances. These instances inherit the ID and wireframe color from the source object.