Sometimes I regret the fact that I got into Japanese Selvedge denim a little too late. This is one of the awesome collaborations I missed on, and I hope they bring it back.
The weft on these jeans is dyed using several plant dyes in yellow, red and green, which gives them their unique appearance. All the dyes used on these jeans come from plants native to the Okinawa Prefecture, and so does the sugarcane fiber that is used in these jeans (50/50 sugar cane and cotton blend).
More pictures here.
The new sugarcane rainbow okinawas that I own are a lot different, because the warp (instead of the weft) is dyed in rainbow colors before being dyed in indigo.