10 Aristarchus my fellow prisoner greets you, as does Mark the cousin of Barnabas, concerning whom you have received instructions - if he comes to you, welcome him.
11 And Jesus who is called Justus greets you. These are the only ones of the circumcision among my co-workers for the kingdom of God, and they have been a comfort to me. καὶ Ἰησοῦς ὁ λεγόμενος Ἰοῦστος, οἱ ὄντες ἐκ περιτομῆς οὗτοι μόνοι συνεργοὶ εἰς τὴνβασιλείαν τοῦ θεοῦ, οἵτινες ἐγενήθησάν μοι παρηγορία.
14 Luke, the beloved physician, and Demas greet you.In verse 11 the phrase "ones of the circumcision" is often taken to mean simply "Jews", and it is then inferred that Luke was not a Jew. But it is not the case that Aristarchus, Mark, and Jesus Justus were Paul's only Jewish co-workers. What about Prisca, Aquila, Apollos, Mary (Rom 16:6), Andronicus and Junia (Rom 16:7), Crispus-Sosthenes, Silas, as well as Barnabas, Simeon, Lucius of Cyrene, and Manaen (Acts 13:1), and also Lucius, Jason and Sosipater (Rom 16:23)? A further problem is that if Paul really did have so few Jewish co-workers, it would be a remarkable coincidence that they were all in the same city as him at this time.
Clearly the scope of Paul's statement here must be limited in some way. Many take it to refer to only those who were with Paul at the time of writing, but this too is problematic. Firstly, there is nothing in the text to suggest this to the audience. Secondly, Timothy was with Paul at the time of writing (Col 1:1), and he was, by then, a Jew (Acts 16:3). If Rome is the provenance, then Prisca, Aquila, Mary, Andronicus, and Junia were probably also close at hand.
Furthermore there is a good reason to suppose that Epaphras and Luke, who were with Paul, were Jews. Here's why. Paul had to defend himself against the charge of bringing a Gentile into the temple. To do so, he stressed his own Jewish credentials and the piety of his friend, Ananias (see here). Given the nature of the charge against him, it was in Paul's interest to be seen to be surrounded by Jews, not Gentiles. Gentile friends could help Paul most by keeping a low profile. Indeed, the tasks of openly supporting Paul and of testifying in his defence would fall particularly to those co-workers who were particularly strict in their observance of the Law, for their testimony would carry weight. It was expedient that those who spent the most time with Paul should be Jews, and preferably strict ones, because of the optics. This suggests that Luke, who accompanied Paul to Rome, was a Jew. Also Epaphras was particularly close to Paul at the time, because Phlm 23 describes him (metaphorically?) as Paul's fellow prisoner, so he too was probably a Jew. Furthermore there are strong arguments that Luke was Lucius (Rom 16:23), who was a Jew (see my next post and here).
How, then, are we to understand Col 4:11? The problems are solved if, with E. E. Ellis and others, we take the "ones of the circumcision" to refer not to Jews in general, but only to those who observed the law rigorously. This seems to be consistent with usage elsewhere (Acts 10:45; 11:2; Rom 4:12; Gal 2:12; Tit 1:10). If we combine this idea with the insights above, we find that Epaphras, Luke, and Demas were Jews, but not of the strict variety. Aristarchus, Mark, and Jesus Justus may then be the only co-workers of Paul anywhere in the world who were of the strict class. They may have been with Paul in Rome specifically because their presence would help his case against the charge of taking Trophimus into the temple. That is to say, Aristarchus may have travelled to Rome with Paul precisely because he was more strict in his observance of the Law than others such as Secundus, Sopater, or Gaius. Aristarchus, Mark, and Jesus-Justus, being the strict, will have spent much time openly with Paul and this explains why Paul sends their greetings before those of Epaphras, Luke and Demas, and it also explains why Paul says that they have been a comfort to him. Paul could not put in writing that the strict Jews were with him to help his legal case, but that could be one of the details that Paul has asked Tychicus and Onesimus to pass on in the immediately preceding lines (Col 4:7-9).
In conclusion, Col 4:11 does not argue that Luke was a Gentile, but actually supports the view that he was a Jew.
While the analysis above is consistent with the Pauline authorship of Colossians, it does not require it. I argued before that Jesus Justus was fictional.