I say it's green, and then you tell me it's red.
I respond that I'm pretty sure, but I could be wrong. You, however, are emphatic that you are right and refuse to admit even the tiniest possibility that you're wrong.
I then find a picture that shows it is, in fact, green, and you respond with, "oh, whatever, I don't really care." Even worse is when I start to look for the picture and you try and stop me from looking up the picture.
This drives me up a fucking wall! Unfortunately, my wife does this all the damn time.
A variant on this is when (typically on social media) someone says something dumb, gets called on it, and then tries to backpedal by saying, "I was clearly just joking." No you weren't! And even if you were, it wasn't the slightest bit funny!