iFlyChat provides two themes - Light and Dark. In default installation, Light theme is loaded.
To change theme, go to App Dashboard. Here go to Settings -> Theme. You will see a screen like below -
Light Theme will look like this -
Dark Theme will look like this -
Chat can further be customised by changing colors of top header background and text. Also, you can customise color of all over font of chat.
They can be customised from the same place as Theme, refer to the screenshot below -