The Instance Highlight node can be used to highlight a specific instance ID number (figure 1).
Figure 1: The Instance Highlight node used to highlight a specific instanced object from a Scatter on Surface node
Highlight Color - The color for the specified ID to highlight.
Regular Color - The color of all the other instances.
Instance ID - The ID number for the highlighted instance.
Swap Colors - Swaps the highlighted color and the regular color.