Ear tattoos. Super easy if your tattoo Gunnisnt garbageWell, hopefully, he got the deed done and died happy.
In terms of coloration, he looked a lot like she - so if I have to replace him, I'll do so with a bunny that resembles neither Blackberry nor Peanut Bunny, simply for ID purposes. Maybe a CA White? I wonder (but not enough to be motivated to look up) how bunnies are normally ID'd. Ear tags just don't seem practical. Or is it a physical check after those few occasions when they are brought together for mating?