i bring this up certainly not to make anybody feel foolish but to prevent that precise feeling from happening.
be aware of how red your teeth are getting as you drink red wines.
not all red wines, however, will result in making you look as though you've been punched solidly in the teeth but you'll probably experience this with some of your more heavily extracted wines (that is to say, wines allowed-or forced-to have more/longer contact with their skins and pulp so that more color and body are "extracted"). So, full-bodied, dark dark reds (i'm looking primarily at you, california and australia) are more likely to stain your teeth and lips.
of course, some people are more sensitive to this effect than others and even lighter reds will be guilty of marking you.
and, like pointing out if you have an errant fleck of food hanging out where it shouldn't (or a shirt tag sticking out - i don't know why that bothers me like it does), we're going to try to begin delicately pointing this out to you when it happens. we don't want you to look foolish and also we don't want you to leave or go to the restroom and see that you've had a hunk of our delicious pulled pork plastered to your punim or lips and teeth like you've been in a blackberry pie eating contest then displace your embarrassment by blaming us for not bringing your new hues to your attention.
there are some preventative measures one can take to avoid this staining.
drinking water and licking your lips frequently (the latter is tricky as one doesn't want to appear lizard-like or lascivious. avoid making deep eye contact or letting your eyes wander to predictable places as you lick your lips) will help with some discoloration. eating while drinking will work a bit, as well. and, sure, you can always avoid deeply colored red wines but sometimes that's not an option. or maybe carry a mirror or discreetly seek out your reflection in something. (the last one may be perceived as vanity but i suppose, to a certain degree, that's what we're talking about anyway.)
but sometimes, if you tend towards big reds, this chromatic evidence of indulgence cannot be avoided and it's something that we're all just going to have to accept. which is not what you want to say to a cop if, god forbid, you're pulled over.
so, like so many things, enjoy yourselves but be aware.