Scarlet

Matthew 27:31 NASB

31   After they had mocked Him, they took the scarlet robe off Him and put His own garments back on Him, and led Him away to crucify Him.

Leviticus 14:51-53

51 He will take the cedar wood, the hyssop, the scarlet yarn, and the live bird, dip them in the blood of the slaughtered bird and the fresh water, and sprinkle the house seven times. 52 He will purify the house with the blood of the bird, the fresh water, the live bird, the cedar wood, the hyssop, and the scarlet yarn. 53 Then he is to release the live bird into the open countryside outside the city. In this way he will make atonement for the house, and it will be clean.

The scarlet thread is woven in the story of God's redemption of man. It is present in the tabernacle, tied to Rahab's window, and in a robe placed on Jesus just before being led away for crucifixion. 

It is through His blood we are saved.