There is a scholarly article written by a professional historian on the subject here:
http://museumofthemacabre.com/research/essays/white-ghosts/
The Museum of the Macabre is great, they have all kinds of ghost related historical stuff!!!
COMMENTS:
Can i just add that i know you said usually white but i thought i would just say that i saw the ghost/spirit of my dead dog when a few days after he died and what i saw was a blur of the colours he was, merged together, not white. i just thought i would share it.
There are hundreds of White Hart Inns. None have ghosts. Ghosts are fictional.
Use the white ghosts to decorate a pumpkin or hang the white ghosts from the ceiling of your house. White ghosts can also be used as a stencil on paper, cloth or a person's face.
No ghosts are verifiable. Some say there are some.
Ghosts that are white are nice and ghosts that are black are evil. It is said to tame black ghosts into white ghosts is to play a soothing melody on the piano. I have 2 white ghosts and 1 black ghost in my home and i always never get attacked by the black ghost cause everyday i play oracion and its very calming to me and the ghosts so pretty much my home is their home.
Ghosts can be small white blobs (orbs) Mist (ectoplasm) or in the shape of a person (shadow ghost) Orbs are white but ectoplasms and shadow ghosts can be black or grey
Ghosts need a white outline because they are always in dark, otherwise how can we see or realise them? Hee..hee...Hee!
Ghosts don"t exist, but no.
Poltergeist are connected to an indiviual ghosts are connected to an area. A house usually
Ghosts can be small white blobs (orbs), just a randomly shaped mist (ectoplasm) or they can be the shape of a person (shadow ghost) Shadow ghosts and ectoplasms can be grey or black, orbs are always white
No. White lights are not an indication of ghosts.
real ghosts are not white, they usally have a outline of them but thats it, sometimes you might see more. But if your asking why people made cartoon ghosts be white, I think its because you can see them better.
Depressed, usually.