Red strings in Judaism

One of Rabbi Zecharia Holzer's articles revealed many ancient sources for red strings. The articles are available for download here:

Link to the original article (Koveitz Etz Chaim volume 24, 2015).

Link to the response to Rabbi Obadi's letter (includes additional early sources for red strings).

Link to the article regarding the Chassam Sofer's opinion on the color red (Koveitz Etz Chaim Volume 28).