My current setup is wonderful and simple (Hyperion on RPi zero + usb hdmi capture + WS2812B). The issue is when the HDMI source turns off, the LED lights revert to an unexpected color combination. I am assuming these are coming from the actual LED strip and not Hyperion. Look like Hyperion looses control of the LEDs when the signal is lost. Is there a way in Hyperion to turn off the LEDs when the USB capture signal is lost? or even a specific effect.
You could turn off the usb capture. At the remote control page. also on the main page you can turn off the whole system.
Does it display some kind of rainbow ? If that is the case, it is your grabber that sends this picture when it receives no signal. In this case, you have to play with signal detection in the USB capture settings of Hyperion.NG Search on the forum for signal detection, me and some other people already have explained how to deal with it.