That sounds like a system that has the lights in those fans all controlled by a third-party Controller. That unit draws power directly from the PSU via a SATA power output connector, and uses a connection to a button on the case front to make changes in the lighting display. MANY such systems also allow you to change how it operates. Often it works this way: if you hold down the front panel button you use to set the display for at least 5 sec, the Controller stops doing that job by itself and turns over control of the display to a signal it gets from your mobo's ARGB header. THAT signal is what this "other cable" plugged into the mobo 3-pin ARGB header is for. IF your system is designed this way, when you make that change the control of lights becomes whatever you can do with the software utility that came with your mobo. But until you make that long-push change, the third-party Controller module is doing it all according to what button pushes you make.