The squad had a training camp last month and numbers have been thinned down to a final trial later this month in Palmerston North. The New Zealand under-20 team will be picked after this trial.
Renton was not initially picked to trial for the squad but has been called in as the selectors seek some depth in the halfback position.
Renton is only 18, and will still be available to play for the squad next year.
He played for New Zealand Schools last year, is a member of the Otago Rugby Academy, and has joined the Kaikorai club.
Otago has its largest representation in the final trial for many years.
Last year, Dunedin flanker Hugh Blake was the only one to make the Colts, although Pirates loose forward Solomon T-Pole later joined the squad as the injury cover.
Also in this year's final trialling squad is Taieri midfield back Michael Collins, University A outside back Faasui Fuatai, Southern inside back Tei Walden, Green Island lock Jackson Hemopo and Harbour flanker Hadleigh May.
Collins and Hemopo played for Otago last year in the ITM Cup. Highlander Jason Emery, who plays his provincial rugby for Manawatu, is expected to be named in the final Colts squad, as he is young enough. He will not be part of the squad that assembles for the final trial. Hurricanes forward Ardie Savea is another player eligible for the side.
Auckland is believed to be the only other union with as many players as Otago in the final cut.
The Colts side is coached by Wellington coach Chris Boyd, with Waikato coach Chris Gibbes and North Harbour coach Liam Barry as his assistants.
The New Zealand Colts had won every game at the world junior championship since it started in 2008 until they lost to Wales in pool play last year.
They still made it through to the final of the tournament but were beaten by home side South Africa.
The young New Zealanders will be out to reclaim their title at the tournament in France in June.
