ac4ce26d_1_0_Help____Editor__Appearance__Item
[Description] Select this check box to show the hierarchy of tags highlighted with different colors. If this option is enabled, you can define the following options: Levels to highlight: specify the depth of hierarchy to be highlighted. Opacity: specify brightness of highlighting Highlighting is activated when there is more than one tag with the same name in the hierarchy. [Item] 
Enable XML/HTML tag tree highlighting
IntelliJ IDEA 14.1.0 Help :: Editor. Appearance