Is Sea Kings' Blessing legal in Standard, Modern, and Commander?

Sea Kings' Blessing is legal in: Legacy, Vintage, Commander.

What type of card is Sea Kings' Blessing?

Sea Kings' Blessing is an Instant. Its oracle text reads: "One or more target creatures become blue until end of turn."

Instant

One or more target creatures become blue until end of turn.

Set Legends

Rarity Uncommon

Artist Randy Asplund-Faith

Instant Commander Legacy Vintage