Reich emerged as the early favorite after Josh McDaniels stunning reversal last week.
The Colts have hired a talented coaching staff so far and will look to add an offensive coordinator in the ensuing weeks.
Reich spent four seasons as an assistant coach in Indianapolis before moving on the Cardinals, Chargers and Eagles, spending the last two seasons as Philadelphia's offensive coordinator.
According to ESPN, the Colts interviewed New Orleans Saints assistant head coach Dan Campbell on Thursday, Reich on Friday and Buffalo Bills defensive coordinator Leslie Frazier on Saturday.
Reich, who led the Buffalo Bills to the biggest comeback in National Football League history against the Houston Oilers after the Bills trailed 35-3, was the beneficiary of Josh McDaniels changing his mind. Manning has reportedly endorsed Reich as Colts head coach.
Newcastle vs Manchester United: Premier League - LIVE - Dubravka makes debut, Pogba returns
The Portuguese manager said he had been confused by the speculation over Pogba's best role in the side. Newcastle United recorded an excellent 2-1 victory over Manchester United on Saturday.
The Colts have a new head coach.
A widely respected offensive mind, it goes without saying that Reich's hire is meant to appease injured franchise quarterback Andrew Luck.
Reich is best known as the Bills' longtime backup quarterback behind Jim Kelly, but has climbed the ladder in the coaching world since his first job with the Colts in 2006. Reich began his coaching career in Indianapolis.
Offensive coordinator Frank Reich of the Philadelphia Eagles speaks to the media during Super Bowl LII media availability on January 31, 2018 at Mall of America in Bloomington, Minnesota. An announcement could come as soon as Tuesday.