The packaging can be used by producers in the region once an inspector from the Hadong Tea Institute inspects the tea's production and usually tries some of the tea. It is a quality control thing and ensures that someone isn't bringing in tea from a cheaper region and selling it as Hadong green tea (which in Korea would be very unlikely). It also makes sure that the people making the tea actually know what they are doing and won't put out a substandard product that would hurt the image of Hadong green teas.
This generic box indicates that this tea is not a big commercial production but rather a small batch. Selling tea in a generic Hadong green tea box has many benefits.
Firstly, it insures a certain level of quality for the consumer because it was inspected by an official from the Hadong Green Tea Institute.
Secondly, it saves the small producer the costs of designing and producing their own box which, for a small batch of green tea, would be quite costly.
Thirdly, it has some marketing appeal because it has brand recognition- in this case the brand is the actual area or "Hadong Green Tea". When customers see the generic box they know its green tea from Hadong. Hadong green tea is a part of South Korea's geographical indication system that has had much success attaching the area of Hadong to green tea (see this research on a similar affect on Boseong and green tea). Fourthly, the colour of the box indicates the grade of green tea, which can also be quite handy for the consumer.
Ujeon grade is packaged in a blue box, saejak in a camouflage green box, jungjak in a gold/yellow and brown box, and daejak in a bright (normal) green box. The red box is the generic packaging for "Bal hyo cha" (semi oxidized, yellow tea). Other than the change of colour the boxes all pretty much look the same.
It is important to note that productions with their own packaging don't follow this colour code. It is also worthy of note that most western dealers of Korean tea would probably not use this packaging because it has only "Hadong Green Tea" written in English and the rest of the characters on the box are Korean.