I want to add a diagram showing the connection between the dimmer value in openHAB and the color temperature in Kelvin for those who wonder about it like me:
As the diagram shows, it is not linear.
Typical values are then:
warm white: 2700K --> 370 mired --> 62.55%
neutral white: 4000K --> 250 mired --> 27,78%
cold white: 5500K --> 182 mired --> 8,08%