Alright, let's discuss the concept of the Yin and Yang jade. (It suddenly hits me lol)
Please keep in mind that I'm new to K-dramaland, so Idk much about Korean culture. I watch C-drama, and Yin and Yang are supposed to be black and white, right? In this drama, the Yin and Yang Jade is blue and red instead. Cultural differences, I assumed. From an article, I found online: (Korean flag as a reference)
"The red and blue circle in the center is called ‘Taeguk’, the origin of all things in the universe. The central thought is perfect harmony and balance: A continuous movement within the sphere of infinity, resulting in one unit. The blue part of ‘Taeguk’ is called ‘Eum’ and represents all the negative aspects of the balance that is typical for the symbol. The red part is called ‘Yang’ and describes all the positive aspects."
As far as I know from C-drama, Yin also represents female, while Yang represents Male. This explained why Jang Uk chose the red while giving Mu Deok the blue one. Them being together is the perfect strength to balance the universe. Yin and Yang Jade, as explained in the drama, also bless the couple who wear it to live happily together and love each other for eternity. (See what Jang Uk did there? XD goddamn you!! hahaha) "The sphere of infinity, resulting in one unit." Being together every lifetime (reincarnation theory confirmed?), and turn into one when they are together. So fitting, and true to their characters!! They are unstoppable whenever they are together. Anyone with another different interpretation, please share your thoughts.