Saruman of Many Colors

• WOTC Official Reminder Textofficial rules
  Ward — Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player pays [cost].

• WWizards of the Coast2023-06-16
  Official Ruling
  If you cast a spell "without paying its mana cost," you can't pay any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, you must pay those.
• WWizards of the Coast2023-06-16
  Official Ruling
  You cast the copy while the ability is resolving and still on the stack. You can't wait to cast it later in the turn.
• WWizards of the Coast2023-06-16
  Official Ruling
  If you don't have an enchantment, instant, or sorcery card in your hand, you won't be able to pay Saruman of Many Colors's ward cost.
• WWizards of the Coast2023-06-16
  Official Ruling
  You don't choose a target for Saruman of Many Colors's ability at the time it triggers. Rather, a second "reflexive" ability triggers when one or more cards are milled this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
• WWizards of the Coast2023-06-16
  Official Ruling
  If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.
• WWizards of the Coast2023-06-16
  Official Ruling
  If the spell you cast has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Rulings via Scryfall