Colley, 27, has been linked with several clubs this summer including Southampton.
But it is Celtic who have come forward with the first real offer for the Gambian international.
The Scottish champions have offered €2.5m for a loan deal with an obligation to buy Colley for €6.5m.
However, there is still a considerable distance between Celtic and Sampdoria in negotiations.
Samp want to sell Colley for at least €10m/€11m to make a captial gain of €5m/€6m on the former Genk player.
Talks could continue because Celtic boss Neil Lennon has put Colley at the top of his list of priorities.
Colley has made 55 appearances in his two years at Sampdoria and last season started 30 games in Serie A.