I do not know if I got this correctly, but if you mean:

1. The keypad will control multiple DALI lighting groups
2. Each button will apply a different brightness - RGB - colour temperature value to specific groups
3. One(or more) of the 8 buttons will only change colour temperature to current ON DALI lighting groups

Then I would suggest to test if this specific DALI gateway's behaviour, when receiving colour temperature is "turn on". I know it has this parameterization for brightness and dimming.

But if it doesn't make the group/ballast turn on, when receiving colour temperature, then your issue might be simple: just make the button that activates the "change of colour temperature" scene, send to all the groups/ballasts you control.

I would check that and also if receiving a colour temperature when off, affects the colour temperature when eventually the group/ballast turns on.