Due solely to supply and demand factors, there is a premium for duvets and pillows containing such fill. In a case where a consumer knows that they will not be using a translucent covering, they may want to consider the darker colour for cost savings.
Colour
The colour of Down & Feather ranges from very white to almost black. Generally though, the majority of the down and feather available is off white or dark grey and the colour depends on the exact species of bird the Down & Feather originated from. Some common names for darker Down and Feather are "silver," and "grey."
Colour does not affect the quality, including warmth and insulating properties, of down and/or feather. In fact, some of the best qualities of Down & Feather are only available in a darker colour. However, most people still prefer white fill because of the fact that it does not show through and darken a light coloured duvet cover.