I was talking about a circle in which only neighbouring nodes are connected: +---+ / \ + + \ / +---+ For 6, for exampl

I was talking about a circle in which only neighbouring nodes are connected: +---+ / \ + + \ / +---+ For 6, for example. This thing is two-colourable, while one with 5 nodes is only three-colourable. That's the instability I was referring to.