You will not be able to set these in one action. You will need to set x_zwave_values.Color_Switch_targetColor_0
to 0 in another action to turn the warm white channel off, and likewise x_zwave_values.Color_Switch_targetColor_1
to 0 to turn off the cold white channel. The intensity of these channels can be set by setting other values up to 255.
It should be possible to set x_zwave_values.Color_Switch_targetColor
with a JSON string, but that is not currently supported in ZWaveJSController. That would allow you to set everything at once. I will work on it.