Bemidbar 

במדבר

The Sages describe the unique banners that each tribe possessed, the distinctive color of each banner, and the drawing that adorned it. 

Each and every prince had an emblem and a banner. The color on each and every banner corresponded to the color of the gems that were on Aaron’s heart, on the breast piece worn by the High Priest. It is from these banners that kingdoms throughout the world learned to prepare national banners with unique colors on each and every banner…. The tribe of Reuben’s stone was a ruby, its banner was red, and mandrakes were drawn on it (see Genesis 30:14). Simeon’s stone was a topaz, its banner was green, and Shekhem was drawn on it (see Genesis 34:25). Levi’s stone was an emerald; its banner was one-third white, one-third black, and one-third red; and the Urim and the Tumim was drawn on it (see Exodus 28:30).  Judah’s stone was a carbuncle, the color of its banner was an image of the heavens, and a lion was drawn on it (see Genesis 49:9). Issachar’s stone was a sapphire, its banner was midnight blue, and the sun and the moon were drawn on it, based on the verse: “From the children of Issachar, possessors of understanding of the times” (I Chronicles 12:33). Zebulun’s stone was a clear quartz, the color of its banner was white, and a ship was drawn on it, based on the verse: “Zebulun shall dwell at the shore of seas” (Genesis 49:13). Dan’s stone was a jacinth, the color of its banner was like a sapphire, and a snake was drawn on it, based on the verse: “Dan shall be a serpent” (Genesis 49:17). Gad’s stone was an agate, the color of its banner was not white and not black but a blend of black and white, and a military camp was drawn on it, based on the verse: “Gad, a troop shall slash his enemies” (Genesis 49:19). Naphtali’s stone was an amethyst, the color of its banner was like unclouded wine that is red but not dark red, and a doe was drawn on it, based on the verse: “Naphtali is a doe let loose” (Genesis 49:21).  Asher’s stone was a beryl, the color of its banner was similar to a gem with which women adorn themselves, and an olive tree was drawn on it, based on the verse: “From Asher, his bread is fat” (Genesis 49:20).<source>(<i>Bemidbar</i> <i>Rabba</i> 2) </source>