Sent in by Chris, he has a few settings that can a Mac more dyslexic friendly.
To get white on black text in apps and menus https://support.apple.com/en-us/HT208976
The get your mac to read back any on screen text that is selectable set up this short cut key:
System preferences -> Keyboard -> Shortcuts -> App Shortc…
click “+” (below the list on the right)
Application = “All Applications”
Menu Title= “Start Speaking”
Keyboard Shortcut =
Select any text on screen then press the key combination you set up.
Warning, this only works on native MacOS application and if you press the buttons, having not selected text it will read the whole document and won’t stop!
Bonus feature, want to dictate to you mac?
Place the curser where you want the text, double tap the “fn” key and start speaking.
press “fn” once to stop.
More info on dictation here; https://support.apple.com/en-gb/guide/mac-help/mh40584/mac
Note: Correct as of Mac OS 11.6 Big Sur