Colomba returned to Reggina in 1999, and stayed in Calabria for three seasons, with a relegation in 2001 (after having lost a playoff match to Verona) and a successive promotion in 2002. In the 2002/2003 season, Colomba had a somehow turbulent Serie B experience at fallen giants Napoli, with a sacking and a successive recall, and a disappointing fifteenth place as a result. The next year saw Colomba making his third comeback at Reggina, but he is fired after the eleventh matchday and replaced by Giancarlo Camolese. The 2004/2005 season started with Colomba at the helm of newly-promoted Serie A side Livorno, but abruptly ended in January, when he was sacked and replaced by Roberto Donadoni. In October 2005, a Serie B team in danger of relegation, Avellino, called him to replace Francesco Oddo; however, Avellino finally lost its place to Serie B after two playoff matches lost to AlbinoLeffe.
Colomba returned to coach in December 2006, when he was appointed to replace Marco Giampaolo at the helm of Serie A club Cagliari Calcio. He was fired on February 26, 2007 following a 2-0 home defeat to Lazio.
On July 19, 2007 he was announced as head coach of Serie C1 club Verona. However, Verona had a very poor start in their Serie C1 2007-08 campaign, with no wins in the initial seven league matches, and a shock 1–2 defeat against Legnano led the club management to sack Colomba on October 8, 2007.