Pakistan Army has followed British Army rank system since its independence from British Empire in 1947. However, crown in the ranks has been replaced with a star and crescent, which symbolizes the sovereignty of Government of Pakistan.
Colonel in Pakistan Army is equivalent to a captain in Pakistan Navy and a group captain in the Pakistan Air Force. Like other armies, this rank is higher than a lieutenant colonel and lower than a brigadier.
References
Colonel (Pakistan) Wikipedia(Text) CC BY-SA