"tail -f" with highlight

tail maillog -f | grep -E ": 550|: 554" | perl -p -e "s/(550|554)/\e[1;46;1m$&\e[0m/g;"

0	all attributes off
1	bold
32	foreground green
40	background black

Colors

This vector holds the colors used for SGR control sequences parameters 30 to 37 \(foreground colors) and 40 to 47 (background colors).

Parameter		Color
30	40	black
31	41	red
32	42	green
33	43	yellow
34	44	blue
35	45	magenta
36	46	cyan
37	47	white