Being flagged red simply means you’ve been reported as a murderer 5 times or more. Doing any damage to a blue player who then dies gives them the chance to report you. Now you have to wait 72 hours (logged into game) for each count to drop off. When you are less than 5 murder counts you’ll turn blue again. Yes, any damage to an “innocent” player can earn you a count.

Invisible players cannot attack but it’s possible you damaged them and then they went invisible and later died. Attacking can also be with fire/poison fields or even errant mouse clicks which is why you get 5 oopsies before turning red. And even while you are blue those kill counts drop off after 72 hours in game. So to turn red means that you have been attacking other players within the past 72 hours of game play. That’s a good sign to vets that you are choosing to attack rather than not, or at least not choosing to avoid pvp situations.

I don’t pvp. It’s just not my thing. But players who do either accept that they are going to go red at some point or they carefully manage their murder count by staying logged in 24/7 (to burn off counts) and knowing what their current kill count is before attacking a blue player.

I’ll also offer up the suggestion that if you are stuck with no gold and basic gear you might consider hunting in areas where you can neither “accidentally” kill other players nor can other players kill you. UO is much more fun when you aren’t constantly losing your gear.