The Korean flag as we know by today was designed on the 25th of January in 1950. The name Taegeukgi or in Korean 태극기, is deflected by Taegeuk 태극 the Korean labeling for the Chinese Taiji principe aka Chinese philosophy.
The white of the flag stands for purity and peaceableness. The colors blue and red are called Eum and Yang and are the Korean pendants to the Chinese Ying and Yang. Red is Yang and blue is Eum. The combined symbol stands for the universe and the four surrounding black trigrams are part of the I Ching writings, which symbolize as follows:
Sky: stands for spring and grace
Water: stands for winter and wisdom
Fire: stands for autumn and modesty
Earth: stands for summer and justice