I’ve always thought that Colin’s performance in Rebel Heart was lost to the annals of time, but it’s not at all! Granted, there doesn’t seem to be any good quality videos of it, but it’s definitely viewable!
His part is in Episode 1, when Ernie Coyne (the main character) visits
Northumberland Road. Colin’s character is a young lad (not even 16, according to a comment by another character) named Rowe (though he’s never referred to by name, it’s listed in the credits). He doesn’t speak on camera, though he does speak off camera - you can recognize his voice, whispering to “Paddy” just before Ernie Coyne enters the room where the two young men are.
There are two uploads of the episode on YouTube (1) (2) - both cued up to Colin’s scene, for your convenience. Be warned: The quality is really bad. But it’s our Colin, and he’s precious, and that makes it wonderful :D