Thank you so much for the very detailed review. I really appreciate it. The project has developed this far because of user feedback and is always evolving. The aim is always to make the user experience better going forward.

I love nitpicking. Here is some context around the colour:
I know what you mean about the colour controls. The primary "Colour" needs to be different as it requires more inputs than all other colours in the app due to the fact this colour is split into 14 shades. These shades are use for everything, like backgrounds, boxe, borders and some text. If you're interested in learning more or would like to discuss details feel free to open discussions on the project repo: https://github.com/zombieFox/nightTab