Select the Mute button.
In Object Property, the Appearance options are for Mute ON. When the mute is activated, the Object color will display.
In Control Button, you can type an ON Label and OFF Label (Ex. Muted and Open). You can also set the Off color.
You can also invert the action of the button so the button function is opposite. In Display Indicator On/Off status, change the Invert setting. True will invert the button functionality.