The entire household in mourning colors.
When Queen Victoria's Albert died at an early age, she never got over the loss of her husband. She was seen wearing black for the rest of her life, and paid such homage to his memory that she had her servants lay out his clothes every day for the rest of her life. She was devoted to him to the end, and the Victorians embraced Victoria's choice of black for mourning as much as her choice of white for weddings.
Mourning was a full-scale event that consumed one's life. Death was not uncommon. After all, having watched Downton, the viewers have watched the end of the Victorian Era, when infant mortality rate was atrociously high, and have seen them come through a World War. We have said goodbye to William, Sybil and Matthew. We are just as aware of death as they seem to be.
Clothing wardrobes were either remade all in black, or dyed to be the suitable color (often being bleached later and then recolored). Black silk crepe was an absolute necessity as long as one could afford it. The staff could come out of mourning much faster, partially because they were expected to keep life moving as normal, and partially because no one wished to pay the extra expense of new clothes. Little reminders, such as a black swatch of cloth around the arm, would not go amiss.
It was of course on the widow that the most obligations of mourning resided. In Victorian times, full black was expected to be worn for the first year, and then one may move to lighter colors such as mauves and grays during the second year. A weeping veil was employed to discreetly hide the face of the widow. This allowed the widow the time to grieve; it gave a cue to society that she was in a delicate state, and I am sure warned many a young suitor to stay away and not bother what could potentially be a wealthy young lady in her time of need.
Mary breaks all rules and regulations after six months by stepping out of black and into purple. Of course, after the country had been through a Great War when no one may have escaped donning black, the rules of mourning loosened. It was also helpful to audience members. We can only sympathize with a lifeless Mary for so long before we want to give her a talking and a quick slap to bring her into reality.
