If i’m not mistaking Tradfri operates similar channels to Hue. If that is the case you should use the Color channel to create 3 items:
Switch - to turn it on and off
Dimmer - to control brightnes
Color - to select colors
Here’s one of my Hue items as an example:
Switch HueGU10Livingroom9Switch "Eettafel spot 5 Switch" (gHueAllSwitch, gLivingroomSalonSwitch, gLightsAll_Sw, gLightsAll, gLightsAutoHomeOn_Sw, gLightsAutoHomeOn_Sw) {channel="hue:0210:0017887ddc49:10:color"}
Dimmer HueGU10Livingroom9Dimmer "Eettafel spot 5 Dimmer [%.0f %%]" (gLivingroomSalonDimmer) {channel="hue:0210:0017887ddc49:10:color"}
Color HueGU10Livingroom9Color "Eettafel spot 5 Kleur" {channel="hue:0210:0017887ddc49:10:color"}
Dimmer HueGU10Livingroom9Colortemp "Eettafel spot 5 kleur Temp" {channel="hue:0210:0017887ddc49:10:color_temperature"}
String HueGU10Livingroom9Alert "Eettafel spot 5 Alert" (gHueAllAlert, gLivingroomSalonAlert) {channel="hue:0210:0017887ddc49:10:alert"}
Switch HueGU10Livingroom9Effect "Eettafel spot 5 Effect" (gLivingRoomSalonEffect) {channel="hue:0210:0017887ddc49:10:effect"}
As you can see… the first 3 items are all connected to the color channel