Depends, are you into appearances? Like anything else, something that stands out such as red gas cost more and serves no different effect than green gas. For some reason it costs more too!
No. Unless you're really serious about your guns, don't bother. Just stick with the green gas. Red gas guns look cool, but they cost a lot more (some are $10,000) and offer no technical improvement.
A red gas gun would only be worth buying if it could be combined with a white and a blues gas gun. This way it would be a great value for the fourth of July.
That depends - how much more expensive is the red one than the other colors? Do you really like red better? Is it your favorite color? Are you just going to cover it with camoflage tape anyway?