Hi Kat! There is a theory that if ghosts/spirits have been showing themselves for a long time, they could in effect sort of fade over the years, sort of like a photograph or a painting does - hence the number of white ladies and grey men and all that stuff. Mind you the idea that white is symbolic of innocence in children is sort of nice!

Another thought - I don't suppose they had sophistocated clothes dyes a few centuries ago and I would imagine that clothing would be in basic colours, unless you happened to have a few quid - I wonder if ghosts of the aristocracy and wealthy people tend to appear more colourful than those of your average everyday person????