I will be watching this thread like a hawk, because the same thing happens to me and it's horrible. It's not just my face that goes red, though, it's my neck and the top of my chest, too It must be so confusing to other people, because it can just happen in the middle of a conversation, seemingly at random, when I suddenly become hyper-aware of the fact that I'm talking to someone and they're looking at me. And I can always feel my whole face heating up, and the knowledge that it's happening just makes it worse. And then I often get really anxious about what the other person is thinking so I start sweating, so I also look disgustingly shiny. Aaaaagh.
I always wear foundation all over my face, not because I'm particularly bothered about my complexion but because it seems to stop the redness from showing, to an extent.
I used to be the same, when I was like 15ish but for some reason it just stopped happening. Think it was more psychological than anything, remember when it first started happening in class when I got picked to read something out loud and because I was nervous I started making a few mistakes and obviously I was embarrased about that, started going slightly red and then someone pointed it and I began to go redder and redder untill the whole class was like "oh my god look how red she is!!" and I had quite a bit to read so I had to carry on through all that, was awful. Became a bit of a problem from then on, I think because I was so cautious of it it made it 100 x worse, got to a point that I even became scared of talking to friends in fear of going red.
But anyway I am not sure what has changed, I just eventually stopped thinking about it, gained in confidence and now its really not an issue, im at Uni now and that involves a lot of talking infront of class and doing presentations and I have never felt myself going red or been slightly concerned about it, infact it was so strange writing this and thinking back to how much of an issue it used to be for me, I really don't understand why it happened.
So basically I don't really have any advice, you will probably just grow out of it. I obviously can't say 'stop noticing it' as that won't work, but try maybe coming up with some distractions? If you feel yourself going red concentrate on something else, like staring at their boobs, or try to look up their nose or start counting backwards or something.