I don't use yellow and red after i got the blue belt but maybe my system can be adapted without too much trouble.
I put a requester chest between the two assembling machines requesting 20k of the yellow limited to one slot. The inserter from the yellow factory is set to work for yellow=0. This way ...

If the demand and production are 0w, the network show full satisfaction. It's annoying when laying lines of power pole into the wild (for outpost or turret creeping) as its much harder to detect the missing pole.
Hope it's not a known bug or a "feature"

Thanks for the update btw