The ectosexual flag.
Ectosexual is an umbrella term for the attraction to people other than oneself. It is the opposite of autosexual.
History
Ectosexual was coined by Deviantart user FlagsforCisHets on July 20th, 2018.
Flag
Alternate Ectosexual flag by HalloAusBerlin.
The flag was coined by Deviantart user FlagsforCisHets on July 20th, 2018. It is the autosexual flag inverted.
Resources
https://www.deviantart.com/flagsforcishets/art/Ectosexual-pride-flag-1-755538721