I really can't think of a single example off the top of my head where someone didn't know who was site staff and who wasn't when presented with a blatantly obvious username color, so I really don't know what you're getting at there. You'd think your typical member with even the slightest bit of common sense knows those particular people's usernames are emphasized for a reason.
Funny thing about 'reason.' It's part of why I've been finding an issue with all this. What is the real reason why a bunch of members who aren't staff suddenly have colored usernames? A specific game? Well, not getting a colored username didn't stop people from playing games before. The entire thing just seems unnecessary. Handing out little rewards for doing whatever arbitrary action is fine and dandy, but I don't think something that could easily confuse people (whether a small or big amount) is really the way to go with it.
Since I first started going to message boards I've immediately associated colored usernames with forum or site staff. Why? Well because that was always the case. It's the standard way to make staff easily identifiable on every message board around these days. Making staff easily identifiable. That's what username colors are usually for. Sure, you can make the point that staff is still easily identifiable if you simply go to the forum staff list, but before all these colored names cropped up everywhere you didn't even have to do that at all. Now for my more personal feelings on the matter.
I've always looked at being forum staff (and subsequently getting a username color) as sort of a privilege. You know, a sign that you actually contributed something of worth and are recognized as someone who is both knowledgeable and helpful to new members. Now I know a perfectly normal member can be both of these things too, but not every normal member needs to be staff, right? I think that's at least one thing everyone can agree with me about.
Custom ranks and titles? Stuff like that is completely alright with me for an ordinary member to have. Colored usernames? That just seems to be a bit too much. I'll make the point again that realistically speaking, most kids who join the forum aren't going to look at the rules, the announcements, or the team listing. If they're actually arsed to use the Personal Message feature to ask for help from someone who they think they could get assistance from, who do you think they might go to? If they've been on a message board before, they'll likely assume someone with a colored username would be the best choice. I know I would.