The crown of Lower Egypt.

The red crown in ancient 

Egypt "Dšrt" is the name of 

the crown of Lower Egypt, and it was red in color representing the red lands on both sides of the fertile green Delta in the Nile Valley.  When they meet with the white crown, which is the crown of Upper Egypt, they form the double crown of Bishnat, who represents the united Egyptian kingdom, which alone pharaoh Narmer around 3100 BC.

 The red crown was also used in hieroglyphs, since it represents the letter "n".  The letter noon was previously represented by the wave of water.  In hieroglyphs, then the symbols are used to write the letter noon. Either horizontally, the "n" was written with a wave of water, or in the vertical writing, the symbol of the red crown was written as representing the noon.