During WWII the Germans used several different styles of canteens, in two different sizes. All branches of the German Armed forces used them. There were no specific models or colors for any type of unit. (The blue covers you see are not Luftwaffe- they are 1950's Berlin Police.) The majority of canteens had a capacity of .75 liters. A larger, 1 liter model was also made.
The canteens consisted of a metal flask, metal or plastic cup, a strap assembly and wool felt cover. There were also "coconut" canteens which had the flask enclosed in bakelite rather than the cover.
Metal flasks and cups were made of aluminum until late 1943, when enameled steel began to appear. Plastic (bakelite) cups were used throughout the War- most were black, but orange and green exist. It appears that all 1 liter canteens were issued with the bakelite cups; the metal cup doesn't fit very well on the shoulders of the larger flask.