The phrase evokes a picture of a garment possessing the colour and high quality of a transparent, brilliant sky. It suggests one thing stunning, ethereal, and presumably related to royalty or excessive standing, given the connotation of a “gown.” The outline implies a visually hanging merchandise of clothes.
Traditionally, associating materials and clothes with the sky’s shade has signified divinity, energy, and wealth throughout varied cultures. Pure dyes producing vibrant blues had been typically uncommon and costly, making such coloured clothes a logo of privilege. The imagery lends itself to inventive representations and poetic expressions, offering a readily comprehensible visible of magnificence and grandeur.