In the past decades, Sake bottles only came in dark colours as the lack of fridges meant that it was imperative to block out UV rays from the sun. This ensured that flavours were retained as well as prevented from undesired aging while shelved.
Blue/Black (High grade): Used for premium Sakes, these bottle colours are more expensive to manufacture.
Clear (Unpasteurized): Clear bottles discourage warming up and also represent the freshness of a seasonal brew.
Green/Brown (General): Most widely used due to affordability and good UV protection for sensitive low-grade sakes. 1.8L bottles tend to come in this colour.
Do note that the purpose of bottle colours still vary between brewers and aesthetics also play a huge part in colour choices nowadays!
Shukuu recommends storing your Sakes below 10 degrees away from the sun and consumed within a year! If a chiller is not available, it is possible to use newspaper to wrap the bottle so as to protect from weather harm!
Today, most breweries are going green and have introduced sanitising machines to encourage recycling of discarded bottles from bars and restaurants. This step forward also has the added benefit of being more cost-effective!
So the next time, you lift a bottle of Sake to examine it, remember that there might just be more to the Sake bottle colour than meets the eye!