I agree, I think grue and bleen were constructed so that green and blue could be redefined in terms of these new time dependent predicates to confuse the fact t

I agree, I think grue and bleen were constructed so that green and blue could be redefined in terms of these new time dependent predicates to confuse the fact that the original colors are not time dependent. In math it is completely normal to write down some complicated formula of time dependent functions and get a result which is independent of time, otherwise there could never be energy conservation for example. There are conventional time dependent predicates like a person's name that nobody has a problem intuiting that induction fails for (many people take their spouse's name after marriage or return to their original name after divorce). It seems like these predicates were invented just to try to confuse what it means for a predicate to be time dependent.