Colak joined the Gers from PAOK Salonika last summer and had a very good initial start before picking up an injury.
He still played 39 times for the Light Blues last season, scoring 18 goals and settling in to the demands of the Scottish game.
Michael Beale is revamping the squad with arrivals and departures for the upcoming season and he is prepared to let Colak go however.
But the Gers are looking to get back most of the £2.5m transfer sum they paid to sign the Croatian striker.
Serie B outfits Parma and Pisa are in the race to sign the 29-year-old frontman.
Beale has already signed forwards such as Cyriel Dessers, Sam Lammers and Abdallah Sima, while Alfredo Morelos and Ryan Kent have left.
The Croat’s probable departure would free up some of the wage bill and make some much-needed funds available to bring in players of the manager’s choice.
It remains to be seen if either of the Italian outfits will meet the Glasgow giants’ desired valuation of the striker.
