Byobu doesn't show the colourful status line

In you case, you have explicitly disabled your status line, as you can tell by the flag file status.disable. You can either remove this file or run byobu-quiet --undo.

It looks like you figured this out and answered your own question in the comment. As to your new question in your comment, we have disabled a few of the infrequently used and hard to maintain menu options, which includes the background/foreground color setting.

To set the foreground/background colors, you have two options now:

• Press ctrl-shift-F5 to set it to a random 256-color combination
• Or manually edit $HOME/.byobu/color.tmux

Full disclosure: I'm the author and maintainer of Byobu.

I had the same issue, and the problem was solved by removing the screen hardstatus and caption (comment out those lines in ~/.screenrc). Byobu will then put its own hardstatus in their place.