Red: You either don’t really care if anyone can see what you’re pointing at or you’re cheap and you use the free pointer you got from a vendor at the expo. Of course, you could be one of those considerate folks who buy very bright red pointers, because you stubbornly like what red looks like even though human eyes are not sensitive to 633 nm. That’s fine.
Green: You want your audience to see what you’re pointing at. Unless you bought a 5+ mW laser (either because you’re showing off or because you didn’t realize how sensitive the human eye is to 532 and bought the brightest laser you could find). In that case, you’re blinding your audience. If you’re going to get a 5 mW laser, get it in red. That’s classy and visible!
Blue: You’re a bad-ass. You don’t care that blue lasers are more expensive and slightly harder to see, you want the audience to know that you’re a real laser jock. (Or maybe you’re worried about leaking 1064 nm from green laser pointers.)
Purple: You’re so bad-ass you’re crazy. You don’t care that the human eye can hardly detect and can’t focus on 405 nm. You want to show that you support Blu-ray.
Yellow: You think blue lasers are soooooo 2009.
Invisible: You have a UV or IR laser pointer? Maybe a tripled or undoubled Nd:YAG? You’re nuts.
Maser pointer: I want one.