Default colour choices

[ClementTsang]

Describe the feature request

Why should we consider this feature request? Describe why, and/or how you think this feature will solve the issue, or overall improve the application:

Despite my, ahem, wonderful default colours, and that you can change the colours if you dislike it, I expect some users won't like my default colours AND don't want to fiddle around with a colour scheme.

As such, adding default, built-in colour schemes to choose from may be of interest.

Additional context/details

Provide any additional context or details here. What needs to be done, why, etc:

• Do this after Add in-app way to change a config file #159.
• Currently some choices we could have are:
  • Default
  • Light mode (for white/lighter backgrounds?)
  • Colourless?