@Kees_van_Gelder from what I can tell “hue” & “saturation” make up the “color” value and the L refers to a “power level” value rather than “color lightness”. It appears that people refer to the colour as HSL which is incorrect as the L does not stand for “lightness” at all. From what I can tell colour is still in HSB and the B is a power level value which would make sense as that would control the brightness of the lights. I hope that makes some sense… my head hurt just writing this! 
This is going to make my rule a bit more complicated too as I need to post to two MQTT topics “color” and “level”. So I have to grab the Colorpicker values convert the the H add it to S and post to “color” and then grab the B and post that to the “level” topic.
FYI
These are the values that can be changed using the ST API
This is the code from the ST App
"colorControl": [
name: "Color Control",
capability: "capability.colorControl",
attributes: [
"hue",
"saturation",
"color"
],
action: "actionColor"
],
"levels": [
name: "Switch Level",
capability: "capability.switchLevel",
attributes: [
"level"
],
action: "actionLevel"
],
"relaySwitch": [
name: "Relay Switch",
capability: "capability.relaySwitch",
attributes: [
"switch"
],
action: "actionOnOff"
],
def actionColor(device, attribute, value) {
switch (attribute) {
case "hue":
device.setHue(value as float)
break
case "saturation":
device.setSaturation(value as float)
break
case "color":
def values = value.split(',')
def colormap = ["hue": values[0] as float, "saturation": values[1] as float]
device.setColor(colormap)
break
}
}
So I’m going to try and create a rule that does the following:
