Haven’t poked an SC1 myself, but my understanding is the original skycontroller colors are functionally identical.
Between SC1 and SC2 it’s the entire controller shape and how it connects to the tablet or phone, with SC2 it’s via cable from controller to device only, no more connect via wifi, said to reduce interference and increase bandwidth available to the drone and controller. They also removed the HDMI output from sc1, and the GPS chip, the controller now relies on GPS from the phone.
Because wifi is no longer used to connect to the controller (only the cable is used ) wifi should always be turned off on your device ( and off on any nearby devices too for that matter ) to prevent interference when using sc2.
There are two models of the SC2, the original which had a larger two cell battery with silver joysticks and a newer one with black joysticks which has a smaller 1 cell battery. This can be a problem with android devices as they try to draw a charge from the USB port on the SC2. IOS devices refuse to draw a charge from the SC2.
For what it’s worth, you can charge the sc2 while using it, which I’m told you couldn’t do with sc1.
From what I’ve seen on the old youtubes the effective range between sc1 and sc2 is the same, 2 is smaller more ergonomic while sc1 is bigger and less fidgety to put a tablet in.
With the sc3 it’s no longer compatible with anything other than anafi right now, and they’ve changed the top wheels to up/down sticks that detect how hard you press them ( like a single direction joystick ). The power button is gone, it turns on when you flip open the phone holder/antenna. No more A and B buttons.