Micky Adams' men continued where they left off in Saturday's eye-catching victory at Crewe to blow away their League Two opponents at a windy Withdean.
It took Brighton only two minutes to seize the initiative. Adam Virgo was totally unmarked at the far post as he headed in a free-kick from former Colchester team-mate Kevin McLeod.
The lead was nearly doubled seven minutes later when Nicky Forster headed against the bar from McLeod's corner.
Brighton only had to wait until the 28th minute to double their lead with a superbly-crafted goal.
Dean Cox's pass inside was laid off on the volley by Glenn Murray into the path of Forster and he finished emphatically for his second goal in as many games.
Virgo nodded in his third in two matches in the 35th minute with a soaring header from another McLeod corner.
Matt Richards, back on loan from Ipswich, got in on the act two minutes before the break with his first goal for the club which was a 20-yard free kick bent around Barnet's defensive wall.
The second half was always liable to be an anti-climax but it proved costly in disciplinary terms for both teams.
Barnet had defender Kenny Gillet sent off in the 69th minute for attempting to head butt Murray.
The Brighton striker was booked for his part in the incident and he also saw red five minutes from time for kicking the ball away after conceding a free-kick.
The only other blemish for Brighton was a first-half knee injury sustained by the influential McLeod, although he is expected to be fit for Saturday's visit of Bristol Rovers.