If you are referring to the colours/styles used to render notes/exported files then I've attached the org file defining the built-in themes.
For the UI colours these are defined in the app code itself. I've attached the assets file - there is an individual JSON file per colour. If I get time I'll see if I can get this into a more usable format - but my time is a little constrained at the moment by lock down and small children.
Thanks Matthew. I was indeed referring to UI colours. I just want to study a colour scheme and compare it with a custom scheme I am building, to see where I am going wrong. My goal is to define a light theme, more or less Solarised-like, with more clearly defined separators and sharply contrasting buttons, and subtle differences in background colour to bring separate elements like the navigation bar, tab bar, agenda list, search and text boxes into relief.
Is there a way at the REPL to dump the default colours, preferably to a file?