Red shows up as red here (every other colour shows as red as well ). It's seems daft to me, I'm sure "colour abuse" is not a major problem, every other forum seems to manage ok.
The color that shows up is based on the style you are currently using.
Just use the highlight bbcode instead (color follows the same rules as that). For example [high]Test[/high] is written as [disable][high]Test[/high][/disable]