When you're preparing a map for a presentation or export, how your drawings look matters as much as what they represent. Giraffe gives you direct control over the visual style of every shape and line you draw — fill colour, line colour, and opacity — through the Appearance widget in the Property Palette.
With a geometry selected, the Appearance Properties are displayed in the properties palette. Every geometry with a Usage assigned also inherits the default visuals from that Usage, and you can override them in the properties panel.
Click on any appearance preset in the appearance widget to apply that preset to the selected geometry, or input new values for number sliders. The changes will apply instantly.