Throne of Eldraine's chosen color is not "Blue" available.
Steps
If able, activate
Throne of Eldraine's first ability by tapping it, adding ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) that can only be spent to cast blue monocolored spells.
Cast
Mystic Speculation with buyback by paying ({2} magic symbol) ({U} magic symbol) , targeting
Displacer Kitten.
Displacer Kitten triggers, blinking
Throne of Eldraine. Choose "Blue" as it enters the battlefield.
Resolve
Mystic Speculation, causing you to scry 3 and return it to your hand.
Repeat.
Notes
Once you have infinite mana to cast Whim of Volrath, you can either name different colors and/or target other permanents.
Results
Infinite LTB.
Infinite ETB.
Infinite storm count.
Infinite blinking of nonland permanents you control.
Infinite magecraft triggers.
Infinite colored mana that can only be spent to cast monocolored spells.