Berets have been used by the Bundeswehr for many years now. Each color represents a different branch/position of the soldier, and we've got several to choose from.
Shell is 100% wool, liner is 100% cotton.
Here are the correlating branches with colors available:
Green = Panzer Grenadier, Jager and Wachtbattalion.
Light Red = Military Police (Feldjager), Artillery, and Combat Support Corps.
Dark Blue = Medical Corps.
Navy Blue = Multinational Corps, Officer Cadet Battalions, Navy and Luftwaffe Security units.