After a bit of research on the sort of Sheets, blankets etc that would be on medieval beds I found contemporay pics showing beds with either very expensive richly coloured or cheap plain bedcovering. but a lot, rich or poor had either off White or pure white Sheets and pillows.
Seeing as These are "middle class beds, I went for the off White Sheets and pillows and to add a bit of colour variety made the covers (or Cloaks ) a different colour.
