OnePlus CEO Pete Lau has said on Weibo that the OnePlus 9 series of smartphones will launch with Oppo's ColorOS Android skin in China. Up until now, OnePlus phones came with HydrogenOS in China, and OxygenOS in the rest of the world.
Lau has also said that phones currently running HydrogenOS will continue to receive support. The OnePlus 9 series is set to launch globally on March 23, while China will see a launch event on March 24.
Both OnePlus and Oppo, along with Vivo and Realme, are owned by Chinese conglomerate BBK Electronics.