The HighlightedVertices command returns a list (which may be empty) of the vertices of a graph G that have been highlighted.

A vertex is considered to have been highlighted if it is to be drawn with a color other than the default.

$\mathrm{with}\left(\mathrm{GraphTheory}\right)\:$

$G≔\mathrm{CompleteGraph}\left(5\right)\:$

$\mathrm{HighlightedVertices}\left(G\right)$

$\mathrm{HighlightVertex}\left(G\,\left\{1\,4\right\}\,''PaleGreen''\right)$

$\mathrm{HighlightedVertices}\left(G\right)$

$\left[1\,4\right]$