Day blue muslin is the classic daytime-sky backing — hang it outside a window and the room reads like a bright blue day, whatever the weather is actually doing. It's one of the traditional backdrop colors every stage has leaned on for decades, and it doubles as a tinted bounce in a pinch. Sizes run from the 4'x4' slip-on up to a 20'x20', all sewn in the USA by LA Rag House. Sunshine on a roll of cloth.