Homebrew PCBs

FeCl would normally be a light or dark tan color.  Black or green means 
it's spent.  The cheapest thing to try is to add some hydrogen peroxide 
to it, which will convert some or all of the dissolved copper into a 
cupric chloride etchant (emerald green).  If that doesn't work, you'll 
have to add some hydrochloric acid, effectively making an acid/peroxide 
etchant that happens to have some spent FeCl in it.

I've used old etchant that wasn't spent and it works just fine; it's not 
the age that counts it's how much you've used it.