This functionality allows defined colour values to appear in the legend even if the related values do not exist in the data. This option is only available for chart types that can display a Legend, please refer to the following list of Chart Types for clarification:
Bar/Column/Area chart
Stacked Bar/Column/Area chart
100% Stacked Bar/Column/Area chart
Spline/Step Area chart
Line/Spline/Step Line chart
Scatter/Bubble chart
Waterfall charts
Column Range charts
Pie/Doughnut
Pie/Doughnut Variable Radius
Spider/Radar/Wind Rose
Funnel/Pyramid
We’ve created a short video that covers this functionality: