Color Chooser is a Gantry-Admin based control interface which, through simple controls, allows you to change all color and style elements of the template, such as text and background color.
Access the Color Chooser from Admin → Extensions → Template Manager → rt_zephyr_j15 → Settings

You can control 7 sections of the template, in 4 different aspects:
Color Chooser Sections
Section Controls

Configuration: Background Controls

MooRainbow & Transparent Mode
Click on the color icons to trigger the MooRainbow popup. Pick any color or transparent.
Theses settings are not directly affiliated with the Color Chooser portion, but affect the template styling nevertheless.

If you use 2,3 or 4 columns in Fusion, you will need to increase the Drop-Down Width (px) value in the menu item settings.