Luca Filippi was fastest in GP2's first post-season test at Barcelona on Tuesday.
The seven-time race-winner only took part in the morning session before handing his Coloni car over to Italian Formula 3 champion Riccardo Agostini.
Coloni, which will not participate in GP2 in 2013, dominated most of the day, with Daniel de Jong second fastest behind team-mate Filippi in the morning and then quickest of all in the afternoon.
It was not a flawless day for the squad, though, as Filippi caused a red flag by spinning and stalling at Turn 5 just after topping the times.
The morning top five was completed by three 2012 GP2 drivers trying out different teams, with Nigel Melker third for champion squad DAMS, long-time iSport man Marcus Ericsson fourth for Trident, and Stephane Richelmi having a run with Lotus in fifth.
Ericsson was second behind de Jong in the afternoon, with European Formula 3 and F3 Euro Series champion Daniel Juncadella next up for Rapax.
Juncadella was just ahead of Stefano Coletti, who has already signed a 2013 Rapax deal.
Caterham protege Alexander Rossi was fifth for the Formula 1 squad's GP2 arm.
In addition to Juncadella, other junior single-seater luminaries trying GP2 at the test included Auto GP champion Adrian Quaife-Hobbs with Rapax, plus GP3 champion Mitch Evans and title rival Daniel Abt, who stayed with their respective Arden and Lotus squads.