HierarchicalClustering`

HighlightStyle

is an option for DendrogramPlot that specifies the style for highlighted clusters.

Details and Options

To use HighlightStyle, you first need to load the Hierarchical Clustering Package using Needs["HierarchicalClustering`"].
Valid settings for HighlightStyle are Automatic or a list of Graphics directives.
The default setting HighlightStyle->Automatic highlights clusters in Green.

Dendrogram highlighting the top 2 clusters in Blue:

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