Currently it uses whatever tmux's default foreground color is set to. For someone using the tmux solarized theme this is orange. A failure background of bright red with orange text is almost impossible to read.
I've added an option to set the foreground color defaulting it to white.
Add option for tmux message foreground
Thanks for the pull request. I've changed it to support a different foreground color per message type, as it's the same with the foreground color. Also the missing specs have been added.
I like to release a new Guard version this week, I just need some feedback on #327, as it seems to work fine and is ready to merge.