From the Portal Wiki
There is an unused alternate backpack icon for the Bot's Beret that can be found in the files of Portal 2. This version of the beret is black instead of the red version as seen in the game.
- This style of beret is actually a Basque-styled beret, introduced in France and Spain during the 19th century. They're mostly worn as part of the uniform of many military and police units worldwide, as well as by other organizations.