A symbol of royalty
the Holy Bible

--Esther--

And Mordecai went out from the presence of the king in royal apparel of blue and white, and with a great crown of gold, and with a garment of fine linen and purple: and the city of Shushan rejoiced and was glad. (8:15)

--Ezekiel--

[Which were] clothed with blue, captains and rulers, all of them desirable young men, horsemen riding upon horses. (23:6)

End of Quotes