OnePlus re-added Photochrom color filter to latest update of OxygenOS 10.5.10. Photochrom color filter becomes popular in social medias that it can see through black metals and some objects. Based on some experiences, it can see through even black-colored clothes.
Some people said that this can intrude personal privacy and thus, OnePlus removes this filter in OxygenOS update 10.5.9. Although OnePlus said that they will remove this feature in China market only, they accidentally remove in Global Market too.
Now Photochrom filter is back in Oxygen OS 10.5.10 and OnePlus didn’t describe this feature in update change logs. If your OnePlus is in 10.5.9 Oxygen OS and cannot use Photochrom filter, you should update to 10.5.10 to use the filter again.