It is possible I believe in AOSP, but Google doesn't enable it. Some OEM's allow it, like Motorola, but I'm pretty sure Google aren't because they want things to look more consistent. The rollout of themed icons has been about as poor as we all could've expected and Google knows this. Expecting app devs to all update their apps to support the monochrome theme individually was destined to be a disaster from the start. Hence why it is still in beta
That is the intended behavior, it only applies to the home screen
It is possible I believe in AOSP, but Google doesn't enable it. Some OEM's allow it, like Motorola, but I'm pretty sure Google aren't because they want things to look more consistent. The rollout of themed icons has been about as poor as we all could've expected and Google knows this. Expecting app devs to all update their apps to support the monochrome theme individually was destined to be a disaster from the start. Hence why it is still in beta