1. A method of operation of a blood detection system comprising: obtaining an input image frame with a camera; extracting image blocks from the input image frame; and calculating an overall blood probability of the image blocks, wherein the overall blood probability is between 0% and 100%, inclusive, including: calculating a red color dominance probability, calculating a red color deviation probability, and calculating a red color colorfulness probability, wherein the overall blood probability is calculated by taking a product of the red color dominance probability, red color deviation probability and the red color colorfulness probability.