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".
Redshirts people support Thailand's ex prime minister, Thaksin Shinwatra.
This search keyword, "redshirts", is very popular now in twitter. Opposite groups some time call them "red buffaloes" as "buffaloes" in Thai means "stupid". This is an insult but ... it's a fact.