How to create a ShellyRGBW item?

The manual of the Shelly RGBW says following:

shellies/shellyrgbw2-/color/0/set accepts a json payload described below:
{
“turn”: “on”, /* bool, can be set with on and off commands /
“red”: 0, /
red brightness, 0…255, applies in mode=“color” /
“green”: 0, /
green brightness, 0…255, applies in mode=“color” /
“blue”: 255, /
blue brightness, 0…255, applies in mode=“color” /
“white”: 0, /
white brightness, 0…255, applies in mode=“color” /
“gain”: 100, /
gain for all channels, 0…100, applies in mode=“color” /
“effect”: 0 /
applies an effect when set */
}

How should look the MQTT item in openhab ?

The power on / off command works this way:

Switch Shelly_5 “RGB Terrasse” [ “Switchable” ] { mqtt=">[broker:shellies/shellyrgbw2-111111/color/0/command:command:*:MAP(shelly.map)],<[broker:shellies/shellyrgbw2-111111/color/0:state:
MAP(shelly.map)]" }

hope this will help

i have tried to copy your setup to my raspberry openhab installation.

But i get this error when i wanna change the color in the sitemap and nothing happens.
Any ideas ?

2019-02-24 19:55:47.390 [ome.event.ItemCommandEvent] - Item ‘Down_front_left_color’ received command ON

2019-02-24 19:55:47.518 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule ‘HSB value to RGB color value’: 1

2019-02-24 19:55:48.067 [ome.event.ItemCommandEvent] - Item ‘Down_front_left_color’ received command ON

2019-02-24 19:55:48.143 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule ‘HSB value to RGB color value’: 1