The couple had planned to attend last year's ceremony on September 17 but Mrs Colton went into labour that day.
"[I was] hoping she was a few days' late. But as it happened she decided to be born two hours before the ceremony started, so it made it a little tricky to make it at that time," Mrs Colton said.
It meant baby Casey, now 5 months old, became a New Zealand citizen before her parents.
"She decided that she didn't want to be left out, that she was going to be the first in the family to become a full Kiwi," Mrs Colton said.
The ceremony began at 7pm with Mayor Adrienne Staples welcoming the candidates.
Candidates were invited to swear on oath or make an affirmation of allegiance, after which Ms Staples presented them with their citizenship certificate and a small gift of recognition, which was a local book.
South Wairarapa District Council chief executive officer Jack Dowds then read a message of congratulations from the Department of Internal Affairs.
Ms Staples presented baby Casey with a nikau palm, a native New Zealand plant, in recognition of the fact that she was the reason her parents missed the last ceremony.
Also among the new citizens were: Vaughan Robinson, Danny Doherty, William Taber, Ligo Falaniko, Mary Huestis, Roxanne Buddle, Aleki Ohi, Linda Burgess, Robert Burgess, Sonja Jacobs, Salmon Jacobs, Lipine Makaohi, Nichola Adams, Petrus Jacobs and Monja Jacobs. Candidates were American, British, Tongan, Samoan and South African.