Work before the true Master

Paul is speaking to household servants here - people whose work was unseen and whose masters were often unjust. He does not tell them the work does not matter. He tells them who they are actually working for.
And the word he uses for that is loaded. In Paul's ethical instruction there is a distinct pattern in how he uses Lord, kyrios: "All of life is lived in the Lord and to the Lord." Chris Tilling's point sharpens it - the way Paul relates believers to Christ is the way a Jew related Israel to YHWH, and "no other figure of any kind, apart from YHWH, was related to in the same way." So "you are serving the Lord Christ" is not a motivational line. It is a claim about who Christ is.
Scripture links:
- Colossians 3:23-24 - "Whatever you do, work heartily, as for the Lord and not for men, knowing that from the Lord you will receive the inheritance as your reward. You are serving the Lord Christ."
- Colossians 3:17 - The verse that frames the whole household section.
The work is not beneath notice. You have simply been reporting to the wrong person.