All four players were restricted free agents.
Colon is entering his fifth season with the team after he was drafted in the fourth round in 2006 out of Hofstra. He has started 50 consecutive games at right tackle.
Gay will enter his fourth year with the Steelers. He was drafted in the fifth round in 2007 out of Louisville and started 14 games last season, making a career-high 78 tackles.
Spaeth also will enter his fourth year with the Steelers after being drafted in the third round in 2007 out of Minnesota. He has 27 receptions for 195 yards and four touchdowns.
Sepulveda is another four-year pro. He was drafted by the Steelers in the fourth round in 2007 out of Baylor.
The Associated Press contributed to this report.