Comment 1 for bug 568967

Here, put this in an executable ~/.byobu/bin/100_uname:

#!/bin/sh
printf "\005{= bw}%s\005{-}" $(uname -r)

The \005 is the escape sequence.

{= bw} says blue background, white text.

{-} says undo the last color change.

See the screen(1) manpage, search for "Colors" to find color codes.