gb, aka Greenbar, is a command line filter which, by default, inverts every other line of its input.
In this way, it's reminiscent of greenbar paper.
% tail -f /var/log/httpd/access_log | gb
or to highlight lines that contain the word "named":
% tail -f /var/log/syslog/daemon.log | gb named
John P. Speno email@example.com
Credit to M. Sirota for the original idea and awk implementation.