Been playing with the Hue API and I see it by design, you just have to understand what’s going on. Below is a result of a GET from the bulb. The OH “brightness” channel, and the Brightness setting in the OH “color” channel are one in the same, they change one value in the bulb, “bri”. I misspoke, both values update correctly in HB.
The bulb operates in two different mode as I suspected. You can see that below under “colormode” which is currently set to “hs”, the other mode is “ct”. The bulb sets this automatically depending on what you send it. The bottom line, is the color picker in HB will give you complete control of the bulb by allowing you to set Hue, Saturation, and Brightness (HSB). The “color_temperature” and “brightness” channels exist for convenience. The “brightness” channel just another way to change the B value in HSB. “color_temperature” is a little more complicated. It adjusts just the H and S, but limits the colors you will see to shades of whites (in the bulb, “colormode” changes to “ct” when you adjust this slider.
What confused me was the following: I would slide the “color_temperature” to get some white light. Then I would want some color, so I would open the color picker and choose a color from the outside ring…nothing would happen! Why? because it did not occur to me to adjust the Saturation, the middle left slider. When you are in the color picker, you are in full manual control. You must consider all three settings, HSB. Hope this helps somebody 
“state”: {
“on”: true,
“bri”: 137,
“hue”: 16800,
“sat”: 72,
“effect”: “none”,
“xy”: [
0.4144,
0.3977
],
“ct”: 299,
“alert”: “none”,
“colormode”: “hs”,
“reachable”: true
},
“type”: “Extended color light”,
“name”: “Hue color lamp 1”,
“modelid”: “LCT007”,
“manufacturername”: “Philips”,
“uniqueid”: “00:17:88:01:10:31:a9:26-0b”,
“swversion”: “5.38.1.14919”
