IKEA GU10 RGB led with deCONZ, issue when choosing white and white temperatures

Hi all

I’m trying to work with some Ikea GU10 RGB lamps.
I have created a group in HA with 3 lamps.
When I turn them on with a call service node, I would like to have always a cold white.
And I’m doing it with

{
    "rgb_color": [
        255,
        218,
        146
    ],
    "brightness_pct": 85
}

I’m using Alexa to manage this light, the Alexa Smart Home node passes a HUE value for all colors and a kelvin value when I ask for a white.

What I’m not able to do is to go back to a white from a color or to go back to a cold white after I asked for a warm white.
Also, after turning on in white color, as above, if I turn just brightness to another %, then when I ask for full brightness, I don’t get same white (almost cold), but a warm one…

This is what I’m doing when a white is requested

msg.payload =
{
data:
{ 
    "kelvin": msg.colortemp
}
}
return msg;

and this is what I’m doing when I request a color

msg.payload =
{
data:
{ 
    "rgb_color": [
        msg.payload[0],
        msg.payload[1],
        msg.payload[2]
    ]
}
}
return msg;

getting the RGB value from the color-convert node.

I tried to use the rgb_color values with kelvin values in the same data, but I get this error

Error Message: two or more values in the same group of exclusion 'Color descriptors' @ data[<Color descriptors>]"

What should be the correct way to do it?

Thanks