OnePlus after releasing the OxygenOS Open Beta 5 and 6 last month has now released OxygenOS Open Beta 7 for OnePlus 6. The latest update brings some notable features such as the Video Enhancer which enhances colors of your phones display while watching videos so you can experience better viewing on your device. You can find the Video Enhancer feature under Settings -> Display.
The Open Beta 7 update also brings OnePlus Roaming which works like a virtual SIM which lets you surf the internet without having a local SIM card in all regions, but it can only be used for data not for calls. You can find the OnePlus Roaming feature under Settings -> Wi-Fi & Internet -> OnePlus Roaming.
The incremental update is now available via OTA and OnePlus 6 users who are already using any previously released Open Beta on their device should expect the OTA update on their OnePlus 6 any time soon.
However, if you want you can also check for the update manually by going to phones Settings/System update.
Since this is an open beta update you might experience some bugs and issues after installing the update on your device.