Taken from the propensity of security officers on the original Star Trek series (who typically wore red uniform tops) to be killed in the epsiodes' pre-opening-credits teasers.
Taken from Star Trek the Original Series, where the security guards wore red, one always 'beamed down' from the spaceship to planets on exploratory missions and always died first. Always.
Don't ever wear a red shirt on a space mission!
"Nahh, the blonde'll die first, they always do in horror movies".
Redshirt is another name that refers to underage girls (typically between the ages 16-17).
They're "a part of the team" = you can check them out, but "they cannot play" = you can't have sex with them because that's illegal.
"Yea, definitely going to be scouting her for the upcoming season"
"Yea, I wonder what her 40 (yard) time is looking like.."
"She's definitely going to be a starter one day."
"Bitch is going to the SEC with that talent."