highlightColumnColor property
Fill colour painted across the highlightedColumn, behind the grid lines
and events. Defaults to a subtle translucent white wash so setting
highlightedColumn alone is visible on the default dark plannerBackground;
override it for a different emphasis (e.g. a brand "today" tint, or a darker
wash on a light background). Ignored when highlightedColumn is null.
Implementation
Color highlightColumnColor;