A while ago I went to Peru and noticed the modern day Quechua use the rainbow flag as the flag of the “Inca”. (Midly amusing to anyone who’s been to SF where it has different conitations 
) Does this have a historical origin is there any documentary evidence of the Inca using a rainbow flag before/during the Spanish conquest ? Or is it actually modern invention ?
Check out some information here :
Apparently originally used as a rebellion flag several centuries back.
Also, the Gay Pride Rainbow Flag has six (or eight) stripes, though it is very similar otherwise.
http://www.crwflags.com/fotw/flags/index.html - best vexillology website there is (one of the better websites, period).
My understanding was that a particular version of the rainbow flag - which you likely saw - is specifically for the city of Cuzco, Peru.