Why does this give me a red wire in Logisim?
Most probably you reset the simulation, but you have no running clock.
So the NORs get 0 on one of their inputs, and ERROR on the other, since their default output value is this. As long as this does not change, the NORs cannot output any other value, because 0 OR ERROR is still ERROR.
Start the clock via the menu &quot;Simulate&quot; - &quot;Ticks enabled&quot; or Ctrl-K.
As soon as one of a NOR's input becomes 1, its output will be 1, too. And the first R-S flip-flop will be error-free. In the second clock phase the second R-S flip-flop will be error-free.
You can watch this step-by-step if you let the clock tick just once. See the menu or type Ctrl-T.
Note: This is not a bug in Logisim, nor in your circuit. Actually I would expect this behavior.