I found a good Markdown reference at https://www.markdownguide.org/
- I suggest to skip Getting started
- Basic Syntax and
- Extended Syntax are worth your time
Underline, font color and size as well as a different alignment can be done with BBCode
For colors I usually refer to this color table
Edit:
- That BBCode reference lacks the [details] and [spoiler] tags - the former should be use now instead of [spoiler2]
- I’d be wary to use HTML - I could not scroll my now deprecated class table on my mobile phone, which is possible in the current HTML-free version