Comment 28 for bug 1599453

oops, adding .notebook.header breaks the preferences window...but you could use:

.terminator-terminal-window .notebook.header

You could also add some transparency to the background of the scrollbar, sort of like "background-color: alpha($color, $percent)", but I think it'd be really hard to get it to match up exactly with the terminal. Also since each VTE can have different transparency, that could get really tricky.