I went with my then 12 year old on the Ausden coach in 2017. As we arrived at the ground we were greeted by 2 lads aged about 11, circling the coach on bikes giving it the middle finger. My lad had colours on and we went for a little walk to get something to eat, but soon enough we had 3 coppers come over to us and insisted on escorting us all the way back to the ground.
You go into the cage near the away turnstile with the coaches nearby and you might hear a bit of abuse and rattling of the cage, but it was heightened last time because of their last minute winner against a Prem team, when they were League 1. The early part of the journey home, in slow moving traffic, things were bouncing off the coach and bottles smashing all over the road in front of us for a while, so it was a bit crazy, but again it was mainly the context of the result that day I think.
I don’t wear colours, but if I did, I personally wouldn’t at Millwall as it has a unique feral feel in the air. It’s always been a ground, like a few others, where I just keep my head down and don’t say anything to the natives. Some mates of mine though have said they’ve mixed with some of their fans pre-match and they’ve been great.
Edit: This game is still one of my son’s all time favourite away day experiences (Not for the result obviously) and we’ve been to 100s. 😂🙈 But we came to no harm I guess and weren’t personally involved in the trouble that day.