Add this CSS to HelloTabPane:

.tab:selected {
    -fx-background-color: linear-gradient(from 50% 0% to 50% 100%, #58595b 0%, #58595b 60%, #363435 95%);
}
 
.tab:selected .tab-label {
    -fx-font: 11pt "Comic Sans MS";
    -fx-text-fill: #f8c27f;
}

The font should return to system default when the tab is no longer selected. The fill resets, but not the font.

See also https://forums.oracle.com/forums/thread.jspa?threadID=2338837&tstart=0
See also http://mail.openjdk.java.net/pipermail/openjfx-dev/2013-February/006094.html