In an interview in Shonen Jump Magazine, Tite Kubo revealed the reasoning behind Bleach's title:
The title wasn't Bleach when Tite Kubo decided to draw a story about Shinigami. This was before he drew the one-shot manga that appeared in Akamaru Jump. The weapon wasn't a sword, but a scythe. Only Rukia had a scythe and the other characters used guns. At that point, the title was Snipe (as in "Sniper"). Right before he started drawing, he began to think that a sword would be better and realized he couldn't use Snipe as a title anymore. He began looking for a title that grasped the bigger picture. Shinigami are associated with the color black, but it would have been boring to use "black". "White", on the other hand, can suggest black as a complementary color. So Tite Kubo chose "Bleach" to evoke the impression of the color white.