Philips Hue Dimmer Switch to change rgb lights

I have Philips Hue Dimmer Switch (RWL022) working in zigbee/deconz. The 4-button version.

Switch turns on and off rgb led strip. Also dimming up and down works.
So I have manage to set 3 out of 4 buttons to work.

What kind of code do I need to get the fourth button to change rgb colors on ledstrip?
Ledstrip is also connected throug zigbee/deconz.