This skin defines colors and defaults for Gantt charts.
You will need to import the gantt.iuml file.
@startuml
!includeurl https://raw.githubusercontent.com/TheIconic/PlantUML-skins/master/src/gantt/gantt.iuml
'...define your gantt chart...
@enduml
See samples folder for examples and syntax.
You will find almost all features used in the Kitchensink.
You can also consult the PlantUML documentation for gantt charts for syntax documentation and more examples.