The Feed icon is for indicating that a web feed is available on a web page. It was originally invented for the use of RSS, but it is also common for Atom and other web feeds now. The icon is normally orange, with hex code #FA9B39. The original icon was created by Stephen Horlander, a designer at Mozilla.
Stephan Horlander was responsible for the orange color of the icon. 
The excerpt says the icon is normally orange which does not necessarily mean always. And although the information does say Stephen Horlander was the original designer, the color is not mentioned. 