Re: red or yellow dice
When you roll the red or yellow dice once in an attempt to complete a task, can you again use these exact same (either one or both) of these dice to roll to complete another/next task (or, if failed the first time, the same task) without having to discard that item card that enabled you to acquire and use the red or yellow dice? Or is it used for only one roll?
It's in the rules, page 9.
Using Items & Spells
Each die added by either a Common or Unique Item remains in
the pool until it is set aside after failing to complete a task or it
is used to complete a task. In any event, the die is removed from
the dice pool at the end of the active player’s turn.
So, they are not used just for one roll, they remain in your dice pool for your turn.