4 pin RGB header pinout and signal

[MeltingPoint]

I've been out of the loop for quite some time and there's not a lot of info online about these rgb headers. My motherboard doesn't have any rgb headers but I have a coolermaster masterair pro fan that comes with a standard 4-pin rgb connector. What is the pinout of these things and what type of signal is coming from a motherboard or rgb controller that controls the led?

 

Edit:

It seems that the pinout is 12V-G-R-B. How is the brightness, hence color combination controlled? I assume it is most likely done through duty cycle/pwm but I can't see how it is done in a common anode config of the rgb header. Is the pwm signal supplied through the respective G, R, B pins? Does the fan motor and leds share a common cathode/ground through the 3 or 4 pin fan header?

 

OR

 

Are the G-R-B pins connected to a low-side switching circuit on the motherboard or controller?

[Unimportant]

3 hours ago, MeltingPoint said:

It seems that the pinout is 12V-G-R-B. How is the brightness, hence color combination controlled? I assume it is most likely done through duty cycle/pwm but I can't see how it is done in a common anode config of the rgb header.

The common anode is connected to 12V and the R, G and B pins are switched to ground in a PWM system or a variable current sink for a linear system. Low side switching is typically easier to implement then high side switching for PWM systems as is low side current sensing for linear systems.

[MeltingPoint]

3 hours ago, Unimportant said:

The common anode is connected to 12V and the R, G and B pins are switched to ground in a PWM system or a variable current sink for a linear system. Low side switching is typically easier to implement then high side switching for PWM systems as is low side current sensing for linear systems.

Yes I was able to light up all leds by tying the rgb pins to ground with resistors. I'm thinking pwm is most likely used for higher efficiency and more precise brightness control