Knife into the white, red knife out
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Knife into the white, red knife out
  Explanation: Mean it takes to kill blood, hands-on hard. Red Knife: a bloody knife.
  Source: Qing Cao Xueqin's "Dream of Red Mansions," the seventh back: "Do not say anything else and I can; to say anything else, we White knife in, knife out of the red!"
No. 2
  词 目 白刀子进,红刀子出
  发 音 bái dāo zǐ jìn,hóng dāo zǐ chū
  释 义 指要杀人见血、动手拼命。红刀子:带血的刀子。
  出 处 清·曹雪芹《红楼梦》第七回:“不和我说别的还可;再说别的,咱们白刀子进去,红刀子出来!”