`HighlightGraph`¶

HighlightGraph[g, spec] returns the graph g with the vertices and edges named by spec drawn in the highlight style — red, by default.

The highlight is a styling only: the graph itself is unchanged.

$ wo 'VertexList[HighlightGraph[Graph[{1 <-> 2, 2 <-> 3}], {2}]]'
{1, 2, 3}

Exactly one vertex is drawn red.

$ wo 'StringCount[ExportString[HighlightGraph[Graph[{1 <-> 2, 2 <-> 3}], {2}], "SVG"], "rgb(255,0,0)"]'
1

Edges can be highlighted too, and a bare part needs no list.

$ wo 'StringCount[ExportString[HighlightGraph[Graph[{1 <-> 2, 2 <-> 3}], 1 <-> 2], "SVG"], "rgb(255,0,0)"]'
1

Style[part, directives] inside the specification picks the colour for that part, which is how a graph is coloured by a per-vertex quantity.

$ wo 'g = Graph[{1 <-> 2, 2 <-> 3}]; StringCount[ExportString[HighlightGraph[g, {Style[1, Green], Style[3, Blue]}], "SVG"], "rgb(0,255,0)"]'
1

A subgraph highlights all of its vertices and edges at once.

$ wo 'g = Graph[{1 <-> 2, 2 <-> 3}]; StringCount[ExportString[HighlightGraph[g, Subgraph[g, {1, 2}]], "SVG"], "rgb(255,0,0)"]'
3

HighlightGraph¶