To set up the display of the Category Tree to your needs you can select a background color and define the font type, size and color.
To change the display:
1. SeSelect Cumulus / Edit > Preferences.
2. Click Category View Sets.
3. Under Set, select the View Set you want to edit.
4. Click Category Pane.
5. Make your selections:
• To change the background color, click the button next to the Background Color field.
• To change the font, click the button next to the Font field. – Changing the font color also affects the color of the square and triangle symbols in the category tree.
NOTE: Font Settings are Operating-System Specific! Cumulus uses different font settings depending on the operating system the Client runs on. Changing these settings in a Category View Set on a Windows Client will not take effect with Clients on OS X, and vice versa. To customize Category View Sets to have the same look and feel both on Windows and OS X, you have to perform appropriate changes twice, on a Mac Client as well as on a Windows Client.
• To change the default display of the Category pane, you can enable/disable various display options. You can activate the option to display the number of records assigned to the category right next to the category name. You can decide which master categories are to be displayed in the drop-down list and which master category will be displayed when the View Set is selected.
NOTE: These are only general options for the display of categories. Which categories are actually displayed depends also on the user permissions set in the User Manager and Live Filtering settings.
Cumulus / 
Edit > Preferences. 
button next to the Background Color field.
button next to the Font field. – Changing the font color also affects the color of the square and triangle symbols in the category tree.