I actually don't see this too often luckily, the clueless people are usually apprehensive about running a new piece of equipment so they might read the manual, or in many cases they put way too much oil in. It's usually the distracted/over confident people who end up running straight fuel in the thing thinking they used mixed gas but switched their cans. A common one I see is people think the mix ratio is 50/50 gas to fuel instead of 50:1.
I try to avoid goof-ups now by only keeping mixed gas in the garage.
With that said, for me I ALWAYS look for color when I'm pouring gas in. I don't know of any 2-stroke oil that isn't colored, and even at 50:1 it's still readily visible.
I grew up with blue oil, and I'm use to mixed gas being blue. With that said, since my "highest-value" 50:1 item is my Echo trimmer, and Echo red armor(or Echo canned fuel) is what I use in everything that takes 50:1.
Since the trimmer, blower, etc all have translucent gas tanks, I just make absolutely sure the gas I see in the tank is red before I start them up.
The mowers are 32:1 and I use blue oil in them(specifically Lawn Boy branded oil) and I always top them up before filling. Even if I know for sure I'm using the can that has mixed gas in it, I make sure I see blue when I'm pouring.
Growing up, we always had at least one LB 2-stroke mower around, so always had mixed gas. The old Craftsman trimmer got the same gas as the mower. The lawn tractor was powered by an 18 HP B&S so we kept straight gas for it. I don't recall ever having a mix-up, and I've gone most of my life with a mix of 2 and 4 stroke around. Now even though I keep two different mixes around(32:1 and 50:1), I'd not worry too much about the mower running a tank of modern synthetic 50:1(some do it for everything) and I'd think one tank of 32:1 in the 50:1 equipment would do less harm than running straight gas.