Please open a file to listen to from your Speechify library.
Click the "Aa" icon to reveal a menu of available options.
Regarding the reading pane color mode, there are Match Device, Light, and Dark options to choose from.
For reading view, there's Original PDF and Reader Mode. Under Reader Mode, you can choose the Font (Avenir Next, Courier, Georgia, New York, Open Dyslexic, SF Mono, SF Pro Text, and Times New Roman), Font size, and Bold Font.
You can set it to Apple themes to PDFs.
And lastly, an option on how pages turn by Scroll, Curl, or Slide.