We have a new life in Christ, and our old life is dead (3:1-4). We are, therefore, called to live consistently with this new identity and put sin to death.
Mortification (5): Since we have a new life ("Therefore"), we must mortify the earthly vices that contradict that new life. Paul lists five such vices. The first two are sexual sins of immorality and impurity. Then comes unrestraint ("passion") and general evil desires, and, finally, an idolatrous form of greed well-known in Colossae. Now, all these forms of evil are "on the earth" and all around us. Thus, we must deal with them and put those appetites to death by starving and suffocating them: "make no provision for the flesh" (Rom. 13:14).
The Past (6-7): We mortify all such sins, because they are the very things that provoke God's wrath. We are no longer disobeyers ("sons of disobedience") who violate the law of God, rebel against Him and incite His anger. That was our past ("you also once walked" and "you were living in them"), and those earthly vices are now behind us. We now walk worthy of the Lord (1:10). As those rescued from darkness (1:13), we await our future glory (3:4) with our heart and mind fixed on Christ (3:1-2), our loving King (1:13-14)!
 "Consider … as dead to" is more forceful in the Greek and is literally "put to death" (ESV, NKJV), or "mortify."
 "The members of your earthly body" is literally "the members on the earth." This is then further explained with the list immediately afterwards (ESV, NKJV). This list names moral vices that are corruptions on earth.
 "Immorality" includes adultery and fornication, whereas "impurity" refers more generally to a wider array of sexual sins. NT warnings about this abound (cf. Matt. 5:28-30; 1 Cor. 6:18-20; Eph. 5:3-7; 1 Thes. 4:3).
 "Passion" includes various forms of sinful unrestraint: anger, violence, abusive speech, addictions, etc.
 “Evil desires” include jealousy, covetousness, selfish ambition, pride, animosity, cynicism, vengefulness, etc.
 "Amounts to idolatry" well captures the intent of the Greek that this was an idolatrous form of greed. Now, even if we don't face the same form of greed, we are called to guard against "every form of greed" (Lk. 12:15).
 "Greed" is articular (literally, "the greed"), unlike the rest in this list. We are not told exactly what this was.