Japanese ceiling lights have standard functionalities for adjusting not only brightness, but also yellow-blue levels. Are simpler (e.g. not full RGB) LED lights like this not as common/affordable in other places? I just realized that I really take them for granted.
I have seen downlights which have a switch to toggle between warm and cool but the switch is not accessible after installation. I imagine the hardest part is just the controls. You’d have to run some data line along with the electrical and then have a special switch which contains the controls. Unless you are willing to go with a wireless remote in which case just get the ikea bulbs for cheap.
I found the cool white too full resulting in a dull clinical grey look and ended up replacing them all with dimmable 150mm warm LED downlights.