XmCascadeButtonHighlight(3) on Linux
The text 52da9154b088, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A CascadeButton and CascadeButtonGadget function that sets the highlight state "XmCascadeButtonHighlight" "CascadeButton functions" "XmCascadeButtonHighlight"