Double click the Power Button to change between temperatures (This can also be done on the session control screen in the Gofire App, by taping on on of the three temperature circles.)
There are three color settings that correlate to different temperatures:
Low - Purple
Medium - Blue
High - Green
You can customize each of the three temperature settings in the Gofire App. Simply press and hold on a temperature circle in the App to reveal the slider. Move your finger along this slider to reach your desired temperature setting.
The video below provides more detail on customizing your temperature settings: