In most countries, walking around the streets wearing a white surgical mask would likely draw stares from those around you. People may even cross the street to avoid whatever plague they think you’re harboring. However, in urban Japan it’s hard to walk down the street without seeing someone in such medical-looking garb, especially during peak allergy seasons.
Despite this, there seems to be an unwritten rule that all face masks should be white. You might see an occasional designer mask with a logo or floral print, but by and large seeing anyone wearing a surgical mask other than white is kind of rare. However, a new brand of mask with the unfortunate name of B.M is challenging this social convention by being pitch black.