Algorithm for display nodes of a particular node based on in-degree and out-degree
If you want to highlight the neighbors:
Use adjacency list representation, where each node has a list of all out-edges out of it, and a list of all in-edges into it.  Then given a node you can rapidly identify what to highlight.
If you want to highlight everything connected to that node (at any distance):
Use DFS to find the set of nodes that are reachable from it.