Our indoor cats watch the outside ferals all the time. Every now and then, Lucky (a 2 year old feral) will sneak into the house when we're not looking (the door is open for the dogs) and wander around for a while. The indoor cats do know him and there is never any arguments between any of them. I believe Lucky does recognize the indoor cats - I've seen him sitting on the outside window ledge looking in on a regular basis. Their behavior when they come face to face shows me that they do recognize each other (by sight and by scent). And yes, I'd love to get Lucky in the house for longer periods of time to try to socialize him further, but he won't have any of it yet.
Is Dygit your red boy or brown/white boy? Sounds like Coal will be putty in his paws! LOL