Really red in the face over nothing? please help :(?

Don't be so embarrassed about it. I'm like that too, any time I get up to talk in front of a class. It's nothing you should wear a ton of make-up over. A lot of people besides you are like this too. The only thing you really can do is just be willing to go up to talk to people much more until you feel you're comfortable with being able to do so and realize that there is nothing to be embarrassed about. If someone does confront you about it again just say you're not used to talking to people. :)