This macro changes the Backlight color of a Logitech device to an RGB value of your choice.
It can be assigned with the type value of backlight or b.

{ type="backlight"|"b", <colors...> [, family=<option>] }

-- Changes the Backlight of the mouse to red.
k.m3 = { type = "backlight", 255, 0, 0 }

The Backlight macro accepts RGB values in 3 different formats: the Red, Green and Blue values as separate numbers or a single string with a valid hex code with either 3 or 6 characters.

-- Cyan with RGB channel values
k.m3 = { type = "backlight", 0, 255, 255 }

-- Cyan with 6 char Hex code
k.m4 = { type = "backlight", "#00FFFF" }

-- Cyan with 3 char Hex code
k.m5 = { type = "backlight", "#0FF" }

Besides the General Macro Options the Backlight Macro offers the following options to customize behavior:

This option controls for which device family the Backlight should be changed. Accepted values are mouse, keyboard or lhc. If the option is not set the family of the device on which this macro was triggered will be used.

-- Even though the macro is on a mouse button, the macro changes the lighting of the keyboard.
k.m3 = { type = "backlight", "#ff0000", family = "keyboard" }