in the korean league, organisations have sister teams. They are under the same ownership, but have separate staff and players. they use this to practice against eachother and stuff and is one of the reasons why all the top teams in the world are korean (regions like NA and EU have a rule preventing this, to make things more balanced). then the colors are just to separate the 2 teams
other examples of this are:
skt t1 k/s
najin white shield/black sword
jin air stealths/falcons