A note to the schematic:
The "wires" from the schematic is there to illustrate where the circuit will be hooked up to the RGB LED on the PCB, the R LED that looks like it is in parallel with it is actual the Red part of the RGB LED.
I have made a spice simulation of my circuit by using LTSpice. This is as a proof of concept before doing the actual hack. It is very nice to be able to test your circuit before buying all the components, in case you got a brain fart, it might save you some time and money ;-)
The optocoupler and voltage source, down in the right corner of the LTSpice window, simulates the push button that will wake up the background LED.
Instead of using the electronic circuit as you propose here, I intend to use one of those TTP223 touch buttons ( https://www.aliexpress.com/item/5PCS-TTP223-Touch-Key-Switch-Module-Touching-Button-Self-Locking-No-Locking-Capacitive-Switches-Single-Channel/32807399108.html?spm=2114.search0302.3.9.761249ffU9YfQ8&ws_ab_test=searchweb0_0,searchweb201602_0_453_454_10618_536_317_537_319_10059_10696_10084_10083_10304_10821_10843_10887_10307_321_322_10065_10068_10301_10103_10884_10820,searchweb201603_0,ppcSwitch_0&algo_pvid=bd7743ee-48b3-4d87-90f8-4fd3cd3b0ef6&algo_expid=bd7743ee-48b3-4d87-90f8-4fd3cd3b0ef6-1 )
Easy connection, one can glue the switch to the outside (back) of the clock.
Yet my problem first how to open the case as I still need to solder the I/O pin to one of the colored display LEDs.