Blue is one of those colours that behaves differently in a bedroom than almost anywhere else in the house. It settles a room. It makes sleep feel more possible. And yet getting the shade right matters enormously because there is a significant difference between a blue that feels coastal and cheerful and one that feels genuinely calm and considered. We have been looking hard at duvet sets across the full range of blues, from the kind of soft slate that works in north facing rooms to deeper navies that hold their own against warm wood tones and natural linens. What we were after was not just colour but quality that improves with washing, a weave that feels good against skin in every season, and sets that look as though they belong rather than arrived. The right blue duvet set does not just dress a bed. It ties together every other choice in the room without making a fuss about it.