Of the three named choices, I'd have to say Colin, definitely. Brad's too old and Orlando just wouldn't cut it. But I have heard rumors about James Bamford, a stunt man, playing Gambit. When I looked at a picture of him, then added in some red and black eyes...well, let's just say I think he'd fit pretty nicely.
James Bamford did the cameo for Gambit in X3, but Singer cut it off the movie. There's a pic of him in Gambit uniform on the first page of this thread. I think he fits the look perfectly and we know he'd be able to do the stunts, but he looks a bit old for Rogue. But then again comic Gambit is older then Rogue, so it could work 😄 ✅