@xris.
Although I understand your reasoning I cannot fully concur with your conclusion.
If the use of an ally required the use of any arbitrary marker simply to count the number of times its skill had been used I would agree with you but since some allies specify a particular marker (stamina or sanity) it leaves the question in doubt, since there is no reason to choose one type of marker rather than another to simply mark that an ally's skill has been invoked.
Our reasoning is that invoking an ally's skill is the result of the player's character using whichever attribute was specified, mind or muscle, to coerce that ally. Hence if the character lacked the necessary marker, due to the particular attribute being reduced below two, he would not be able to invoke the ally's skill. One the other hand, we also decided that the character's markers would be returned if the ally was dismissed or had used all of its actions.
Perhaps it is simply a question of which side of
All that is not forbidden is compulsory
one wishes to favor.
...ef
If it was a Green die then it can be added to your dice pool. It it was Yellow or Red, then you can spend an Item to add it to your dice pool.