I omitted context because the comment was pretty clear and the same advice appears elsewhere e.g in PC Gamer's tips:
"However, if you constantly spend more than is streaming in, you risk crashing your entire economy. When a crash occurs, your income indicator will flash red ... During this time, your Engineers or Constructors will continue to build with what little resources they have to work with, but the rate of production will be extremely slow."
So I wondered about "crashing the economy" (one or both resource streams negative) actual consequences. As mentioned, I can't keep things within the green band - I'm usually underproducing, and if a resource does go green I send engineers to start building stuff and use it up! BUT if there were a penalty for being negative, I'd have to rethink this.
As mentioned, there would be little or no sense to having such a penalty, but I wanted to ask. I've overlooked or misunderstood quite a few things in Ashes, and so have other people.