You have the option of choosing the background theme for your Presentation Mode. You can choose between a "Light" or "Dark" theme.
To choose your Presentation Mode Theme....
1. Sign in to a Session as a Moderator and Click "Session Settings"

2. Click "View and Manage Current Presentations"

3. Click "Change Presentation Configuration"

4. Choose the "Dark" or "Light" Background Option

Examples of Background Options

Light Theme Background

Dark Theme Background