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
Clockspinning with buyback by paying ({3} magic symbol) ({U} magic symbol) , targeting
Throne of Eldraine.
Orvar's first ability triggers, creating a copy of
Throne of Eldraine. Choose "Blue" as its color as it enters the battlefield.