Nexus 6 found has a RGB LED sensor, and you can enable it via Light Flow

Moore, who has yet to obtain a Nexus 6, was able to cobble together a series of steps, via the Android SDK, to enable the trick:


ok it actually seems to work quite well after a bit of experimenting in the adb shell.

You’ll need root but with that try the following:

Choose root mode
run every command as root and
direct mode
Make sure “su”/superuser has access granted for all requests

Then go into lightflow, notification settings and you should have a
“mixer” option. Enable that and you should then see options to set the
red, green and blue leds and also an option to set their brightness.

The brightness is has a 255 max value (0 being off) – (255 max brightness) and it should work.

The led won’t flash but you can mix them together to get different colors. Technically you don’t need to use the mixer but there’s more control with it from what I remember.
​

One thing to be aware of, other than the necessity of Root status, is that several XDA users have mentioned the LED doesn’t flash, which one might assume means pulsate. Why Motorola has actually included this feature but disabled it might sound strange indeed, although it’s important to remember that the original Moto X had a similar light that had the sole purpose of lighting up when the battery was too low to use active display — it’s very possible the purpose here is similar.

Either way, this could potentially be good news for those that are upset that the Nexus 6 doesn’t have a notification light.