Oona, Queen of the Fae

Flying
{X}{U/B}: Choose a color. Target opponent exiles the top X cards of their library. For each card of the chosen color exiled this way, create a 1/1 blue and black Faerie Rogue creature token with flying.

Wilds of Eldraine Commander

Flying
{X}{UB}: Choose a color. Target opponent exiles the top X cards of their library. For each card of the chosen color exiled this way, create a 1/1 blue and black Faerie Rogue creature token with flying.

Zendikar Rising Commander

Secret Lair Drop

Modern Masters

Flying
{X}{UB}: Choose a color. Target opponent exiles the top X cards of his or her library. For each card of the chosen color exiled this way, put a 1/1 blue and black Faerie Rogue creature token with flying onto the battlefield.

From the Vault: Legends

You target the opponent when you activate Oona's ability. You don't choose the color until the ability resolves.