What is the significance of red hair? Some people attribute all sorts of negative characteristics to people with red hair, but the colour of a person’s hair does not indicate their worth in God’s eyes.
Esau gave evidence of an impulsive, careless nature and a hot temper when he later set out to kill his conniving brother (Genesis 27:41). But he mellowed with age and appears to have developed a nobler character when he forgave his brother and sought to live in peace (Genesis 33:4). Redheads, like everyone else, have no excuse for giving in to sinful tendencies and resisting the Lord’s attempts to build character.
The most famous redhead in the Bible is David. He was “ruddy and had beautiful eyes and was handsome” (1 Samuel 16:12, ESV). The word translated “ruddy” could refer to David’s complexion, but some commentators believe it refers to his hair. David could have been redheaded. His character was opposite that of Esau’s. David was “a man after God’s own heart” (Acts 13:22), while Esau was a “profane person” (Hebrews 12:16, NKJV). David was a man of strong passions. When those passions were surrendered to the Lord, they served him well. He fought God’s battles, was a leader of men, and penned most of the psalms. But when those passions were allowed to control him, they led David to deep sin and deception (2 Samuel 11). https://www.gotquestions.org/red-hair-in-the-Bible.html
What is the significance of scarlet thread? In Old Testament times it was the custom to give the first-born son the privileges of the birthright. When twins were being born the midwife would identify the first to be born by tying a scarlet thread round the wrist. In the case of Tamar, when the arm of one of the twins emerged, the midwife tided the scarlet thread round his wrist to identify him as the firstborn. But the arm was withdrawn and then the other twin, Perez was born first. The significance of Perez being born first is that God’s providence had decreed that the Messiah would come through the line of Perez (Matthew 1:3):
The account of twins Perez and Zerah can be found in Genesis 38. Jacob’s son Judah slept with a woman he thought was a prostitute, only to find out later it was his widowed daughter-in-law, Tamar. King David would later descend from the family line of Perez (Ruth 4:18). Matthew 1:3 notes Perez in the line of ancestors of Jesus Christ. https://www.gotquestions.org/twins-in-the-Bible.html
Another significant mention of scarlet thread is in Joshua 2 when the two spies who went to Jericho were kept safe by Rahab:
The spies were hidden in Jericho by Rahab the harlot, who expressed her faith in Israel’s God and protected the spies (see Hebrews 11:31). Rahab allowed the Hebrew spies to escape from Jericho by letting them down through her window by means of a rope made of scarlet thread. As they left, the spies told Rahab, “Tie this cord of scarlet thread in the window” (Joshua 2:18), with the promise that she and her household would be kept safe in the coming invasion. By faith, Rahab obeyed: “And she tied the scarlet cord in the window” (verse 21).
Later, when the walls of Jericho fell down and the Israelites took the city, Joshua commanded that Rahab and her family be spared (Joshua 6:22–23). Marking her home was, of course, the “cord of scarlet thread.” It’s easy to dismiss the colour of Rahab’s rope as mere coincidence, but the scarlet colour is significant. The rope in her window was a sign of her faith and led to her salvation, as she was not destroyed with the rest of Jericho. The scarlet rope—the colour of blood—worked for Rahab much as the blood of the Passover lamb had worked during the exodus: every home marked with blood was spared death that night (Exodus 12:13). God’s mercy and forgiveness of Rahab the harlot was signified by a rope of scarlet thread, which becomes a symbol of the blood of Christ.
Theologians and Bible students sometimes refer to “the scarlet thread running through the Bible.” By this they mean that the Bible’s theme is Jesus Christ and His sacrifice for the redemption of mankind. The blood of Christ runs throughout the entire Bible, symbolically. It is seen in the animals killed in Eden to provide garments for Adam and Eve, the ram that took Isaac’s place on the altar of Moriah, the Passover lamb, the institution of the sacrificial system, the scarlet rope of Rahab, and the thousands of years of sacrifices performed at the tabernacle and temple. The scarlet thread runs all the way to John the Baptist’s declaration, “Look, the Lamb of God, who takes away the sin of the world!” (John 1:29) and to the foot of the cross, where Jesus finally says, “It is finished” (John 19:30).
“Without the shedding of blood there is no forgiveness” (Hebrews 9:22), and that’s why the symbolism of the scarlet thread in the Bible is significant. The scarlet thread is the theme of atonement found throughout the pages of Scripture. https://www.gotquestions.org/scarlet-thread.html
What is the significance of twins: As already mentioned, the birthright would go to the first born son, and the twins born to Isaac and Rebekah are probably the best-known twins in the Old Testament:
Genesis 25:22–26 says, “The babies jostled each other within her, and she said, ‘Why is this happening to me?’ So she went to inquire of the Lord. The Lord said to her, ‘Two nations are in your womb, and two peoples from within you will be separated; one people will be stronger than the other, and the older will serve the younger.’ When the time came for her to give birth, there were twin boys in her womb. The first to come out was red, and his whole body was like a hairy garment; so they named him Esau. After this, his brother came out, with his hand grasping Esau’s heel; so he was named Jacob.”
These two brothers would continue in conflict, with Jacob stealing their father’s blessing and then running away to live with his uncle Laban. However, Jacob would indeed become the stronger of the two brothers, fathering twelve sons who would become the leaders of the twelve tribes of Israel.
There are other twins mentioned in the Bible but without any special significance being attached to them. Source: https://www.gotquestions.org/twins-in-the-Bible.html