The 19-year-old Hornets attacker has returned to the U's for a second spell, after making three appearances for John Ward's side during January and February.
Massey said: "I know what the club and the players are about, having been here for a month before.
"I enjoyed playing here and it was a shame that it got cut short.
"I'm now looking forward to Saturday and the other games coming up."
Massey will be available for Colchester's next eight games and goes into their squad for their home game against Huddersfield Town, tomorrow.
See Friday's Gazette for a full preview of the U's game with Huddersfield and all of the latest Colchester United news.