Using a simple light detector circuit, I tethered the demon lock insert light to the red led I installed in the demon mouth. It's a bit more animated and lights during the attract mode as well:

This circuit is portable (i.e. not hard wired into the pin permanently) so I can re-use the same mod in another pin or create more to use in other pins as well. I first used it in Iron Man to light up the chest light on an IM figure I installed in the game.

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That is an awesome mod!!! I'm still working on something like that for KISS. I have various IR detectors hidden (as best I can) on the pf to detect the ball. They go back to an arduino and trigger different lighting effects on three lengths of neopixels.. It's still a work in progress with the most difficult part being getting the light sequences to look like they are factory installed. I'm not a fan of mods that 'look like mods'.

I have not tried this yet, but the R G B pins are easily accessible on the insert lights in KISS. "In theory", you could read all three on analog inputs into the arduino. From the value read on the input pins, you would have to note which values correspond to each mode color. (Might be able to do it with only one pin if the values for each mode are unique.