Select the node, use "Tools" -> "Select Elements" to select all successors, and finally choose a different fill color for the now selected successor nodes.
To select successors with "Select Elements", switch to tab "Nodes", enable "Use these Criteria" on this tab (and this tab only), set "Select" to "Successors of Selected Nodes" and "Maximal Path Distance" to a high value (e.g. the total number of nodes in your diagram will always work).