Purity has been connected with white. It can be both positive and negative. In soap it is a positive. It has of course been connected with race in a rather negative way. The members of the Ku Klux Klan for example wear white to symbolize purity of race and the desire to keep the races apart.
In Korea and no doubt other parts of Asia white is symbolic of death. Since skeletons are white this does make sense.
The Jolly Roger is a black pirate flag with white skull and white crossbones. It struck fear into sailors and travelers from the early 18th Century onward. The white skull and white crossbones can also be found on some bottles indicating that they contain poison.
White over time has also come to symbolize slavery. It is sometimes easy to forget that other people besides Caucasians (British, French, Italians, Americans) have been slavers. The Aztecs also kept slaves and were into human sacrifice. The Ancient Egyptians, Arab traders, the Chinese at one stage and the Japanese also cannot claim in this regard to have a clean slate. And yet it is the white races and thus white that has come to symbolize one person owning another.
Going back to Ancient Roman times the white flag has been used for surrender which is negative. It has also been used to indicate truce or ceasefire for purposes of negotiation or for the collecting of the wounded from a battlefield.