As far as I can tell the color of the square is determenined by your reputation here on the boards. <--- This button. Looking back at your past post, you had one locked for being nonsense. I'm sure thats where the red square came from.
But seriously look at the posts where you go your negitive reputation and learn from them. Normally there's a reason but if it's just someone being pathetic then don't worry about it, however I don't think this is the case here.