When the Width Selector tool is in use, width markers on the focal strokes of all unlocked paths (selected or unselected, unless the tool preference Show Markers on Selected Paths Only is enabled) are annotated using small red (by default) “bow-tie” shapes lying perpendicular to the path. Markers drawn in a lighter tint are unselected, while those in a darker tint are selected:
Width Selector Marker Annotations